CGRecordLayoutBuilder.cpp revision 14d56ef43ff4921c6749f7340212fbb743fdbb9b
1//===--- CGRecordLayoutBuilder.cpp - CGRecordLayout builder ----*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// Builder implementation for CGRecordLayout objects. 11// 12//===----------------------------------------------------------------------===// 13 14#include "CGRecordLayout.h" 15#include "clang/AST/ASTContext.h" 16#include "clang/AST/Attr.h" 17#include "clang/AST/CXXInheritance.h" 18#include "clang/AST/DeclCXX.h" 19#include "clang/AST/Expr.h" 20#include "clang/AST/RecordLayout.h" 21#include "CodeGenTypes.h" 22#include "CGCXXABI.h" 23#include "llvm/DerivedTypes.h" 24#include "llvm/Type.h" 25#include "llvm/Support/Debug.h" 26#include "llvm/Support/raw_ostream.h" 27#include "llvm/Target/TargetData.h" 28using namespace clang; 29using namespace CodeGen; 30 31namespace { 32 33class CGRecordLayoutBuilder { 34public: 35 /// FieldTypes - Holds the LLVM types that the struct is created from. 36 /// 37 llvm::SmallVector<const llvm::Type *, 16> FieldTypes; 38 39 /// BaseSubobjectType - Holds the LLVM type for the non-virtual part 40 /// of the struct. For example, consider: 41 /// 42 /// struct A { int i; }; 43 /// struct B { void *v; }; 44 /// struct C : virtual A, B { }; 45 /// 46 /// The LLVM type of C will be 47 /// %struct.C = type { i32 (...)**, %struct.A, i32, %struct.B } 48 /// 49 /// And the LLVM type of the non-virtual base struct will be 50 /// %struct.C.base = type { i32 (...)**, %struct.A, i32 } 51 /// 52 /// This only gets initialized if the base subobject type is 53 /// different from the complete-object type. 54 const llvm::StructType *BaseSubobjectType; 55 56 /// FieldInfo - Holds a field and its corresponding LLVM field number. 57 llvm::DenseMap<const FieldDecl *, unsigned> Fields; 58 59 /// BitFieldInfo - Holds location and size information about a bit field. 60 llvm::DenseMap<const FieldDecl *, CGBitFieldInfo> BitFields; 61 62 llvm::DenseMap<const CXXRecordDecl *, unsigned> NonVirtualBases; 63 llvm::DenseMap<const CXXRecordDecl *, unsigned> VirtualBases; 64 65 /// IndirectPrimaryBases - Virtual base classes, direct or indirect, that are 66 /// primary base classes for some other direct or indirect base class. 67 CXXIndirectPrimaryBaseSet IndirectPrimaryBases; 68 69 /// LaidOutVirtualBases - A set of all laid out virtual bases, used to avoid 70 /// avoid laying out virtual bases more than once. 71 llvm::SmallPtrSet<const CXXRecordDecl *, 4> LaidOutVirtualBases; 72 73 /// IsZeroInitializable - Whether this struct can be C++ 74 /// zero-initialized with an LLVM zeroinitializer. 75 bool IsZeroInitializable; 76 bool IsZeroInitializableAsBase; 77 78 /// Packed - Whether the resulting LLVM struct will be packed or not. 79 bool Packed; 80 81 /// IsMsStruct - Whether ms_struct is in effect or not 82 bool IsMsStruct; 83 84private: 85 CodeGenTypes &Types; 86 87 /// LastLaidOutBaseInfo - Contains the offset and non-virtual size of the 88 /// last base laid out. Used so that we can replace the last laid out base 89 /// type with an i8 array if needed. 90 struct LastLaidOutBaseInfo { 91 CharUnits Offset; 92 CharUnits NonVirtualSize; 93 94 bool isValid() const { return !NonVirtualSize.isZero(); } 95 void invalidate() { NonVirtualSize = CharUnits::Zero(); } 96 97 } LastLaidOutBase; 98 99 /// Alignment - Contains the alignment of the RecordDecl. 100 CharUnits Alignment; 101 102 /// BitsAvailableInLastField - If a bit field spans only part of a LLVM field, 103 /// this will have the number of bits still available in the field. 104 char BitsAvailableInLastField; 105 106 /// NextFieldOffset - Holds the next field offset. 107 CharUnits NextFieldOffset; 108 109 /// LayoutUnionField - Will layout a field in an union and return the type 110 /// that the field will have. 111 const llvm::Type *LayoutUnionField(const FieldDecl *Field, 112 const ASTRecordLayout &Layout); 113 114 /// LayoutUnion - Will layout a union RecordDecl. 115 void LayoutUnion(const RecordDecl *D); 116 117 /// LayoutField - try to layout all fields in the record decl. 118 /// Returns false if the operation failed because the struct is not packed. 119 bool LayoutFields(const RecordDecl *D); 120 121 /// Layout a single base, virtual or non-virtual 122 void LayoutBase(const CXXRecordDecl *base, 123 const CGRecordLayout &baseLayout, 124 CharUnits baseOffset); 125 126 /// LayoutVirtualBase - layout a single virtual base. 127 void LayoutVirtualBase(const CXXRecordDecl *base, 128 CharUnits baseOffset); 129 130 /// LayoutVirtualBases - layout the virtual bases of a record decl. 131 void LayoutVirtualBases(const CXXRecordDecl *RD, 132 const ASTRecordLayout &Layout); 133 134 /// LayoutNonVirtualBase - layout a single non-virtual base. 135 void LayoutNonVirtualBase(const CXXRecordDecl *base, 136 CharUnits baseOffset); 137 138 /// LayoutNonVirtualBases - layout the virtual bases of a record decl. 139 void LayoutNonVirtualBases(const CXXRecordDecl *RD, 140 const ASTRecordLayout &Layout); 141 142 /// ComputeNonVirtualBaseType - Compute the non-virtual base field types. 143 bool ComputeNonVirtualBaseType(const CXXRecordDecl *RD); 144 145 /// LayoutField - layout a single field. Returns false if the operation failed 146 /// because the current struct is not packed. 147 bool LayoutField(const FieldDecl *D, uint64_t FieldOffset); 148 149 /// LayoutBitField - layout a single bit field. 150 void LayoutBitField(const FieldDecl *D, uint64_t FieldOffset); 151 152 /// AppendField - Appends a field with the given offset and type. 153 void AppendField(CharUnits fieldOffset, const llvm::Type *FieldTy); 154 155 /// AppendPadding - Appends enough padding bytes so that the total 156 /// struct size is a multiple of the field alignment. 157 void AppendPadding(CharUnits fieldOffset, CharUnits fieldAlignment); 158 159 /// ResizeLastBaseFieldIfNecessary - Fields and bases can be laid out in the 160 /// tail padding of a previous base. If this happens, the type of the previous 161 /// base needs to be changed to an array of i8. Returns true if the last 162 /// laid out base was resized. 163 bool ResizeLastBaseFieldIfNecessary(CharUnits offset); 164 165 /// getByteArrayType - Returns a byte array type with the given number of 166 /// elements. 167 const llvm::Type *getByteArrayType(CharUnits NumBytes); 168 169 /// AppendBytes - Append a given number of bytes to the record. 170 void AppendBytes(CharUnits numBytes); 171 172 /// AppendTailPadding - Append enough tail padding so that the type will have 173 /// the passed size. 174 void AppendTailPadding(CharUnits RecordSize); 175 176 CharUnits getTypeAlignment(const llvm::Type *Ty) const; 177 178 /// getAlignmentAsLLVMStruct - Returns the maximum alignment of all the 179 /// LLVM element types. 180 CharUnits getAlignmentAsLLVMStruct() const; 181 182 /// CheckZeroInitializable - Check if the given type contains a pointer 183 /// to data member. 184 void CheckZeroInitializable(QualType T); 185 186public: 187 CGRecordLayoutBuilder(CodeGenTypes &Types) 188 : BaseSubobjectType(0), 189 IsZeroInitializable(true), IsZeroInitializableAsBase(true), 190 Packed(false), IsMsStruct(false), 191 Types(Types), BitsAvailableInLastField(0) { } 192 193 /// Layout - Will layout a RecordDecl. 194 void Layout(const RecordDecl *D); 195}; 196 197} 198 199void CGRecordLayoutBuilder::Layout(const RecordDecl *D) { 200 Alignment = Types.getContext().getASTRecordLayout(D).getAlignment(); 201 Packed = D->hasAttr<PackedAttr>(); 202 203 IsMsStruct = D->hasAttr<MsStructAttr>(); 204 205 if (D->isUnion()) { 206 LayoutUnion(D); 207 return; 208 } 209 210 if (LayoutFields(D)) 211 return; 212 213 // We weren't able to layout the struct. Try again with a packed struct 214 Packed = true; 215 LastLaidOutBase.invalidate(); 216 NextFieldOffset = CharUnits::Zero(); 217 FieldTypes.clear(); 218 Fields.clear(); 219 BitFields.clear(); 220 NonVirtualBases.clear(); 221 VirtualBases.clear(); 222 223 LayoutFields(D); 224} 225 226CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types, 227 const FieldDecl *FD, 228 uint64_t FieldOffset, 229 uint64_t FieldSize, 230 uint64_t ContainingTypeSizeInBits, 231 unsigned ContainingTypeAlign) { 232 const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(FD->getType()); 233 CharUnits TypeSizeInBytes = 234 CharUnits::fromQuantity(Types.getTargetData().getTypeAllocSize(Ty)); 235 uint64_t TypeSizeInBits = Types.getContext().toBits(TypeSizeInBytes); 236 237 bool IsSigned = FD->getType()->isSignedIntegerType(); 238 239 if (FieldSize > TypeSizeInBits) { 240 // We have a wide bit-field. The extra bits are only used for padding, so 241 // if we have a bitfield of type T, with size N: 242 // 243 // T t : N; 244 // 245 // We can just assume that it's: 246 // 247 // T t : sizeof(T); 248 // 249 FieldSize = TypeSizeInBits; 250 } 251 252 // in big-endian machines the first fields are in higher bit positions, 253 // so revert the offset. The byte offsets are reversed(back) later. 254 if (Types.getTargetData().isBigEndian()) { 255 FieldOffset = ((ContainingTypeSizeInBits)-FieldOffset-FieldSize); 256 } 257 258 // Compute the access components. The policy we use is to start by attempting 259 // to access using the width of the bit-field type itself and to always access 260 // at aligned indices of that type. If such an access would fail because it 261 // extends past the bound of the type, then we reduce size to the next smaller 262 // power of two and retry. The current algorithm assumes pow2 sized types, 263 // although this is easy to fix. 264 // 265 assert(llvm::isPowerOf2_32(TypeSizeInBits) && "Unexpected type size!"); 266 CGBitFieldInfo::AccessInfo Components[3]; 267 unsigned NumComponents = 0; 268 unsigned AccessedTargetBits = 0; // The number of target bits accessed. 269 unsigned AccessWidth = TypeSizeInBits; // The current access width to attempt. 270 271 // Round down from the field offset to find the first access position that is 272 // at an aligned offset of the initial access type. 273 uint64_t AccessStart = FieldOffset - (FieldOffset % AccessWidth); 274 275 // Adjust initial access size to fit within record. 276 while (AccessWidth > Types.getTarget().getCharWidth() && 277 AccessStart + AccessWidth > ContainingTypeSizeInBits) { 278 AccessWidth >>= 1; 279 AccessStart = FieldOffset - (FieldOffset % AccessWidth); 280 } 281 282 while (AccessedTargetBits < FieldSize) { 283 // Check that we can access using a type of this size, without reading off 284 // the end of the structure. This can occur with packed structures and 285 // -fno-bitfield-type-align, for example. 286 if (AccessStart + AccessWidth > ContainingTypeSizeInBits) { 287 // If so, reduce access size to the next smaller power-of-two and retry. 288 AccessWidth >>= 1; 289 assert(AccessWidth >= Types.getTarget().getCharWidth() 290 && "Cannot access under byte size!"); 291 continue; 292 } 293 294 // Otherwise, add an access component. 295 296 // First, compute the bits inside this access which are part of the 297 // target. We are reading bits [AccessStart, AccessStart + AccessWidth); the 298 // intersection with [FieldOffset, FieldOffset + FieldSize) gives the bits 299 // in the target that we are reading. 300 assert(FieldOffset < AccessStart + AccessWidth && "Invalid access start!"); 301 assert(AccessStart < FieldOffset + FieldSize && "Invalid access start!"); 302 uint64_t AccessBitsInFieldStart = std::max(AccessStart, FieldOffset); 303 uint64_t AccessBitsInFieldSize = 304 std::min(AccessWidth + AccessStart, 305 FieldOffset + FieldSize) - AccessBitsInFieldStart; 306 307 assert(NumComponents < 3 && "Unexpected number of components!"); 308 CGBitFieldInfo::AccessInfo &AI = Components[NumComponents++]; 309 AI.FieldIndex = 0; 310 // FIXME: We still follow the old access pattern of only using the field 311 // byte offset. We should switch this once we fix the struct layout to be 312 // pretty. 313 314 // on big-endian machines we reverted the bit offset because first fields are 315 // in higher bits. But this also reverts the bytes, so fix this here by reverting 316 // the byte offset on big-endian machines. 317 if (Types.getTargetData().isBigEndian()) { 318 AI.FieldByteOffset = Types.getContext().toCharUnitsFromBits( 319 ContainingTypeSizeInBits - AccessStart - AccessWidth); 320 } else { 321 AI.FieldByteOffset = Types.getContext().toCharUnitsFromBits(AccessStart); 322 } 323 AI.FieldBitStart = AccessBitsInFieldStart - AccessStart; 324 AI.AccessWidth = AccessWidth; 325 AI.AccessAlignment = Types.getContext().toCharUnitsFromBits( 326 llvm::MinAlign(ContainingTypeAlign, AccessStart)); 327 AI.TargetBitOffset = AccessedTargetBits; 328 AI.TargetBitWidth = AccessBitsInFieldSize; 329 330 AccessStart += AccessWidth; 331 AccessedTargetBits += AI.TargetBitWidth; 332 } 333 334 assert(AccessedTargetBits == FieldSize && "Invalid bit-field access!"); 335 return CGBitFieldInfo(FieldSize, NumComponents, Components, IsSigned); 336} 337 338CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types, 339 const FieldDecl *FD, 340 uint64_t FieldOffset, 341 uint64_t FieldSize) { 342 const RecordDecl *RD = FD->getParent(); 343 const ASTRecordLayout &RL = Types.getContext().getASTRecordLayout(RD); 344 uint64_t ContainingTypeSizeInBits = Types.getContext().toBits(RL.getSize()); 345 unsigned ContainingTypeAlign = Types.getContext().toBits(RL.getAlignment()); 346 347 return MakeInfo(Types, FD, FieldOffset, FieldSize, ContainingTypeSizeInBits, 348 ContainingTypeAlign); 349} 350 351void CGRecordLayoutBuilder::LayoutBitField(const FieldDecl *D, 352 uint64_t fieldOffset) { 353 uint64_t fieldSize = 354 D->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue(); 355 356 if (fieldSize == 0) 357 return; 358 359 uint64_t nextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset); 360 CharUnits numBytesToAppend; 361 unsigned charAlign = Types.getContext().Target.getCharAlign(); 362 363 if (fieldOffset < nextFieldOffsetInBits && !BitsAvailableInLastField) { 364 assert(fieldOffset % charAlign == 0 && 365 "Field offset not aligned correctly"); 366 367 CharUnits fieldOffsetInCharUnits = 368 Types.getContext().toCharUnitsFromBits(fieldOffset); 369 370 // Try to resize the last base field. 371 if (ResizeLastBaseFieldIfNecessary(fieldOffsetInCharUnits)) 372 nextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset); 373 } 374 375 if (fieldOffset < nextFieldOffsetInBits) { 376 assert(BitsAvailableInLastField && "Bitfield size mismatch!"); 377 assert(!NextFieldOffset.isZero() && "Must have laid out at least one byte"); 378 379 // The bitfield begins in the previous bit-field. 380 numBytesToAppend = Types.getContext().toCharUnitsFromBits( 381 llvm::RoundUpToAlignment(fieldSize - BitsAvailableInLastField, 382 charAlign)); 383 } else { 384 assert(fieldOffset % charAlign == 0 && 385 "Field offset not aligned correctly"); 386 387 // Append padding if necessary. 388 AppendPadding(Types.getContext().toCharUnitsFromBits(fieldOffset), 389 CharUnits::One()); 390 391 numBytesToAppend = Types.getContext().toCharUnitsFromBits( 392 llvm::RoundUpToAlignment(fieldSize, charAlign)); 393 394 assert(!numBytesToAppend.isZero() && "No bytes to append!"); 395 } 396 397 // Add the bit field info. 398 BitFields.insert(std::make_pair(D, 399 CGBitFieldInfo::MakeInfo(Types, D, fieldOffset, fieldSize))); 400 401 AppendBytes(numBytesToAppend); 402 403 BitsAvailableInLastField = 404 Types.getContext().toBits(NextFieldOffset) - (fieldOffset + fieldSize); 405} 406 407bool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D, 408 uint64_t fieldOffset) { 409 // If the field is packed, then we need a packed struct. 410 if (!Packed && D->hasAttr<PackedAttr>()) 411 return false; 412 413 if (D->isBitField()) { 414 // We must use packed structs for unnamed bit fields since they 415 // don't affect the struct alignment. 416 if (!Packed && !D->getDeclName()) 417 return false; 418 419 LayoutBitField(D, fieldOffset); 420 return true; 421 } 422 423 CheckZeroInitializable(D->getType()); 424 425 assert(fieldOffset % Types.getTarget().getCharWidth() == 0 426 && "field offset is not on a byte boundary!"); 427 CharUnits fieldOffsetInBytes 428 = Types.getContext().toCharUnitsFromBits(fieldOffset); 429 430 const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(D->getType()); 431 CharUnits typeAlignment = getTypeAlignment(Ty); 432 433 // If the type alignment is larger then the struct alignment, we must use 434 // a packed struct. 435 if (typeAlignment > Alignment) { 436 assert(!Packed && "Alignment is wrong even with packed struct!"); 437 return false; 438 } 439 440 if (!Packed) { 441 if (const RecordType *RT = D->getType()->getAs<RecordType>()) { 442 const RecordDecl *RD = cast<RecordDecl>(RT->getDecl()); 443 if (const MaxFieldAlignmentAttr *MFAA = 444 RD->getAttr<MaxFieldAlignmentAttr>()) { 445 if (MFAA->getAlignment() != Types.getContext().toBits(typeAlignment)) 446 return false; 447 } 448 } 449 } 450 451 // Round up the field offset to the alignment of the field type. 452 CharUnits alignedNextFieldOffsetInBytes = 453 NextFieldOffset.RoundUpToAlignment(typeAlignment); 454 455 if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) { 456 // Try to resize the last base field. 457 if (ResizeLastBaseFieldIfNecessary(fieldOffsetInBytes)) { 458 alignedNextFieldOffsetInBytes = 459 NextFieldOffset.RoundUpToAlignment(typeAlignment); 460 } 461 } 462 463 if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) { 464 assert(!Packed && "Could not place field even with packed struct!"); 465 return false; 466 } 467 468 AppendPadding(fieldOffsetInBytes, typeAlignment); 469 470 // Now append the field. 471 Fields[D] = FieldTypes.size(); 472 AppendField(fieldOffsetInBytes, Ty); 473 474 LastLaidOutBase.invalidate(); 475 return true; 476} 477 478const llvm::Type * 479CGRecordLayoutBuilder::LayoutUnionField(const FieldDecl *Field, 480 const ASTRecordLayout &Layout) { 481 if (Field->isBitField()) { 482 uint64_t FieldSize = 483 Field->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue(); 484 485 // Ignore zero sized bit fields. 486 if (FieldSize == 0) 487 return 0; 488 489 const llvm::Type *FieldTy = llvm::Type::getInt8Ty(Types.getLLVMContext()); 490 CharUnits NumBytesToAppend = Types.getContext().toCharUnitsFromBits( 491 llvm::RoundUpToAlignment(FieldSize, 492 Types.getContext().Target.getCharAlign())); 493 494 if (NumBytesToAppend > CharUnits::One()) 495 FieldTy = llvm::ArrayType::get(FieldTy, NumBytesToAppend.getQuantity()); 496 497 // Add the bit field info. 498 BitFields.insert(std::make_pair(Field, 499 CGBitFieldInfo::MakeInfo(Types, Field, 0, FieldSize))); 500 return FieldTy; 501 } 502 503 // This is a regular union field. 504 Fields[Field] = 0; 505 return Types.ConvertTypeForMemRecursive(Field->getType()); 506} 507 508void CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) { 509 assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!"); 510 511 const ASTRecordLayout &layout = Types.getContext().getASTRecordLayout(D); 512 513 const llvm::Type *unionType = 0; 514 CharUnits unionSize = CharUnits::Zero(); 515 CharUnits unionAlign = CharUnits::Zero(); 516 517 bool hasOnlyZeroSizedBitFields = true; 518 519 unsigned fieldNo = 0; 520 for (RecordDecl::field_iterator field = D->field_begin(), 521 fieldEnd = D->field_end(); field != fieldEnd; ++field, ++fieldNo) { 522 assert(layout.getFieldOffset(fieldNo) == 0 && 523 "Union field offset did not start at the beginning of record!"); 524 const llvm::Type *fieldType = LayoutUnionField(*field, layout); 525 526 if (!fieldType) 527 continue; 528 529 hasOnlyZeroSizedBitFields = false; 530 531 CharUnits fieldAlign = CharUnits::fromQuantity( 532 Types.getTargetData().getABITypeAlignment(fieldType)); 533 CharUnits fieldSize = CharUnits::fromQuantity( 534 Types.getTargetData().getTypeAllocSize(fieldType)); 535 536 if (fieldAlign < unionAlign) 537 continue; 538 539 if (fieldAlign > unionAlign || fieldSize > unionSize) { 540 unionType = fieldType; 541 unionAlign = fieldAlign; 542 unionSize = fieldSize; 543 } 544 } 545 546 // Now add our field. 547 if (unionType) { 548 AppendField(CharUnits::Zero(), unionType); 549 550 if (getTypeAlignment(unionType) > layout.getAlignment()) { 551 // We need a packed struct. 552 Packed = true; 553 unionAlign = CharUnits::One(); 554 } 555 } 556 if (unionAlign.isZero()) { 557 assert(hasOnlyZeroSizedBitFields && 558 "0-align record did not have all zero-sized bit-fields!"); 559 unionAlign = CharUnits::One(); 560 } 561 562 // Append tail padding. 563 CharUnits recordSize = layout.getSize(); 564 if (recordSize > unionSize) 565 AppendPadding(recordSize, unionAlign); 566} 567 568void CGRecordLayoutBuilder::LayoutBase(const CXXRecordDecl *base, 569 const CGRecordLayout &baseLayout, 570 CharUnits baseOffset) { 571 ResizeLastBaseFieldIfNecessary(baseOffset); 572 573 AppendPadding(baseOffset, CharUnits::One()); 574 575 const ASTRecordLayout &baseASTLayout 576 = Types.getContext().getASTRecordLayout(base); 577 578 LastLaidOutBase.Offset = NextFieldOffset; 579 LastLaidOutBase.NonVirtualSize = baseASTLayout.getNonVirtualSize(); 580 581 // Fields and bases can be laid out in the tail padding of previous 582 // bases. If this happens, we need to allocate the base as an i8 583 // array; otherwise, we can use the subobject type. However, 584 // actually doing that would require knowledge of what immediately 585 // follows this base in the layout, so instead we do a conservative 586 // approximation, which is to use the base subobject type if it 587 // has the same LLVM storage size as the nvsize. 588 589 const llvm::StructType *subobjectType = baseLayout.getBaseSubobjectLLVMType(); 590 AppendField(baseOffset, subobjectType); 591 592 Types.addBaseSubobjectTypeName(base, baseLayout); 593} 594 595void CGRecordLayoutBuilder::LayoutNonVirtualBase(const CXXRecordDecl *base, 596 CharUnits baseOffset) { 597 // Ignore empty bases. 598 if (base->isEmpty()) return; 599 600 const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base); 601 if (IsZeroInitializableAsBase) { 602 assert(IsZeroInitializable && 603 "class zero-initializable as base but not as complete object"); 604 605 IsZeroInitializable = IsZeroInitializableAsBase = 606 baseLayout.isZeroInitializableAsBase(); 607 } 608 609 LayoutBase(base, baseLayout, baseOffset); 610 NonVirtualBases[base] = (FieldTypes.size() - 1); 611} 612 613void 614CGRecordLayoutBuilder::LayoutVirtualBase(const CXXRecordDecl *base, 615 CharUnits baseOffset) { 616 // Ignore empty bases. 617 if (base->isEmpty()) return; 618 619 const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base); 620 if (IsZeroInitializable) 621 IsZeroInitializable = baseLayout.isZeroInitializableAsBase(); 622 623 LayoutBase(base, baseLayout, baseOffset); 624 VirtualBases[base] = (FieldTypes.size() - 1); 625} 626 627/// LayoutVirtualBases - layout the non-virtual bases of a record decl. 628void 629CGRecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD, 630 const ASTRecordLayout &Layout) { 631 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 632 E = RD->bases_end(); I != E; ++I) { 633 const CXXRecordDecl *BaseDecl = 634 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 635 636 // We only want to lay out virtual bases that aren't indirect primary bases 637 // of some other base. 638 if (I->isVirtual() && !IndirectPrimaryBases.count(BaseDecl)) { 639 // Only lay out the base once. 640 if (!LaidOutVirtualBases.insert(BaseDecl)) 641 continue; 642 643 CharUnits vbaseOffset = Layout.getVBaseClassOffset(BaseDecl); 644 LayoutVirtualBase(BaseDecl, vbaseOffset); 645 } 646 647 if (!BaseDecl->getNumVBases()) { 648 // This base isn't interesting since it doesn't have any virtual bases. 649 continue; 650 } 651 652 LayoutVirtualBases(BaseDecl, Layout); 653 } 654} 655 656void 657CGRecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD, 658 const ASTRecordLayout &Layout) { 659 const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase(); 660 661 // Check if we need to add a vtable pointer. 662 if (RD->isDynamicClass()) { 663 if (!PrimaryBase) { 664 const llvm::Type *FunctionType = 665 llvm::FunctionType::get(llvm::Type::getInt32Ty(Types.getLLVMContext()), 666 /*isVarArg=*/true); 667 const llvm::Type *VTableTy = FunctionType->getPointerTo(); 668 669 assert(NextFieldOffset.isZero() && 670 "VTable pointer must come first!"); 671 AppendField(CharUnits::Zero(), VTableTy->getPointerTo()); 672 } else { 673 if (!Layout.isPrimaryBaseVirtual()) 674 LayoutNonVirtualBase(PrimaryBase, CharUnits::Zero()); 675 else 676 LayoutVirtualBase(PrimaryBase, CharUnits::Zero()); 677 } 678 } 679 680 // Layout the non-virtual bases. 681 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 682 E = RD->bases_end(); I != E; ++I) { 683 if (I->isVirtual()) 684 continue; 685 686 const CXXRecordDecl *BaseDecl = 687 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 688 689 // We've already laid out the primary base. 690 if (BaseDecl == PrimaryBase && !Layout.isPrimaryBaseVirtual()) 691 continue; 692 693 LayoutNonVirtualBase(BaseDecl, Layout.getBaseClassOffset(BaseDecl)); 694 } 695} 696 697bool 698CGRecordLayoutBuilder::ComputeNonVirtualBaseType(const CXXRecordDecl *RD) { 699 const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(RD); 700 701 CharUnits NonVirtualSize = Layout.getNonVirtualSize(); 702 CharUnits NonVirtualAlign = Layout.getNonVirtualAlign(); 703 CharUnits AlignedNonVirtualTypeSize = 704 NonVirtualSize.RoundUpToAlignment(NonVirtualAlign); 705 706 // First check if we can use the same fields as for the complete class. 707 CharUnits RecordSize = Layout.getSize(); 708 if (AlignedNonVirtualTypeSize == RecordSize) 709 return true; 710 711 // Check if we need padding. 712 CharUnits AlignedNextFieldOffset = 713 NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct()); 714 715 if (AlignedNextFieldOffset > AlignedNonVirtualTypeSize) { 716 assert(!Packed && "cannot layout even as packed struct"); 717 return false; // Needs packing. 718 } 719 720 bool needsPadding = (AlignedNonVirtualTypeSize != AlignedNextFieldOffset); 721 if (needsPadding) { 722 CharUnits NumBytes = AlignedNonVirtualTypeSize - AlignedNextFieldOffset; 723 FieldTypes.push_back(getByteArrayType(NumBytes)); 724 } 725 726 BaseSubobjectType = llvm::StructType::get(Types.getLLVMContext(), 727 FieldTypes, Packed); 728 729 if (needsPadding) { 730 // Pull the padding back off. 731 FieldTypes.pop_back(); 732 } 733 734 return true; 735} 736 737bool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) { 738 assert(!D->isUnion() && "Can't call LayoutFields on a union!"); 739 assert(!Alignment.isZero() && "Did not set alignment!"); 740 741 const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D); 742 743 const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D); 744 if (RD) 745 LayoutNonVirtualBases(RD, Layout); 746 747 unsigned FieldNo = 0; 748 const FieldDecl *LastFD = 0; 749 750 for (RecordDecl::field_iterator Field = D->field_begin(), 751 FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 752 if (IsMsStruct) { 753 // Zero-length bitfields following non-bitfield members are 754 // ignored: 755 const FieldDecl *FD = (*Field); 756 if (Types.getContext().ZeroBitfieldFollowsNonBitfield(FD, LastFD)) { 757 --FieldNo; 758 continue; 759 } 760 LastFD = FD; 761 } 762 763 if (!LayoutField(*Field, Layout.getFieldOffset(FieldNo))) { 764 assert(!Packed && 765 "Could not layout fields even with a packed LLVM struct!"); 766 return false; 767 } 768 } 769 770 if (RD) { 771 // We've laid out the non-virtual bases and the fields, now compute the 772 // non-virtual base field types. 773 if (!ComputeNonVirtualBaseType(RD)) { 774 assert(!Packed && "Could not layout even with a packed LLVM struct!"); 775 return false; 776 } 777 778 // And lay out the virtual bases. 779 RD->getIndirectPrimaryBases(IndirectPrimaryBases); 780 if (Layout.isPrimaryBaseVirtual()) 781 IndirectPrimaryBases.insert(Layout.getPrimaryBase()); 782 LayoutVirtualBases(RD, Layout); 783 } 784 785 // Append tail padding if necessary. 786 AppendTailPadding(Layout.getSize()); 787 788 return true; 789} 790 791void CGRecordLayoutBuilder::AppendTailPadding(CharUnits RecordSize) { 792 ResizeLastBaseFieldIfNecessary(RecordSize); 793 794 assert(NextFieldOffset <= RecordSize && "Size mismatch!"); 795 796 CharUnits AlignedNextFieldOffset = 797 NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct()); 798 799 if (AlignedNextFieldOffset == RecordSize) { 800 // We don't need any padding. 801 return; 802 } 803 804 CharUnits NumPadBytes = RecordSize - NextFieldOffset; 805 AppendBytes(NumPadBytes); 806} 807 808void CGRecordLayoutBuilder::AppendField(CharUnits fieldOffset, 809 const llvm::Type *fieldType) { 810 CharUnits fieldSize = 811 CharUnits::fromQuantity(Types.getTargetData().getTypeAllocSize(fieldType)); 812 813 FieldTypes.push_back(fieldType); 814 815 NextFieldOffset = fieldOffset + fieldSize; 816 BitsAvailableInLastField = 0; 817} 818 819void CGRecordLayoutBuilder::AppendPadding(CharUnits fieldOffset, 820 CharUnits fieldAlignment) { 821 assert(NextFieldOffset <= fieldOffset && 822 "Incorrect field layout!"); 823 824 // Round up the field offset to the alignment of the field type. 825 CharUnits alignedNextFieldOffset = 826 NextFieldOffset.RoundUpToAlignment(fieldAlignment); 827 828 if (alignedNextFieldOffset < fieldOffset) { 829 // Even with alignment, the field offset is not at the right place, 830 // insert padding. 831 CharUnits padding = fieldOffset - NextFieldOffset; 832 833 AppendBytes(padding); 834 } 835} 836 837bool CGRecordLayoutBuilder::ResizeLastBaseFieldIfNecessary(CharUnits offset) { 838 // Check if we have a base to resize. 839 if (!LastLaidOutBase.isValid()) 840 return false; 841 842 // This offset does not overlap with the tail padding. 843 if (offset >= NextFieldOffset) 844 return false; 845 846 // Restore the field offset and append an i8 array instead. 847 FieldTypes.pop_back(); 848 NextFieldOffset = LastLaidOutBase.Offset; 849 AppendBytes(LastLaidOutBase.NonVirtualSize); 850 LastLaidOutBase.invalidate(); 851 852 return true; 853} 854 855const llvm::Type *CGRecordLayoutBuilder::getByteArrayType(CharUnits numBytes) { 856 assert(!numBytes.isZero() && "Empty byte arrays aren't allowed."); 857 858 const llvm::Type *Ty = llvm::Type::getInt8Ty(Types.getLLVMContext()); 859 if (numBytes > CharUnits::One()) 860 Ty = llvm::ArrayType::get(Ty, numBytes.getQuantity()); 861 862 return Ty; 863} 864 865void CGRecordLayoutBuilder::AppendBytes(CharUnits numBytes) { 866 if (numBytes.isZero()) 867 return; 868 869 // Append the padding field 870 AppendField(NextFieldOffset, getByteArrayType(numBytes)); 871} 872 873CharUnits CGRecordLayoutBuilder::getTypeAlignment(const llvm::Type *Ty) const { 874 if (Packed) 875 return CharUnits::One(); 876 877 return CharUnits::fromQuantity(Types.getTargetData().getABITypeAlignment(Ty)); 878} 879 880CharUnits CGRecordLayoutBuilder::getAlignmentAsLLVMStruct() const { 881 if (Packed) 882 return CharUnits::One(); 883 884 CharUnits maxAlignment = CharUnits::One(); 885 for (size_t i = 0; i != FieldTypes.size(); ++i) 886 maxAlignment = std::max(maxAlignment, getTypeAlignment(FieldTypes[i])); 887 888 return maxAlignment; 889} 890 891/// Merge in whether a field of the given type is zero-initializable. 892void CGRecordLayoutBuilder::CheckZeroInitializable(QualType T) { 893 // This record already contains a member pointer. 894 if (!IsZeroInitializableAsBase) 895 return; 896 897 // Can only have member pointers if we're compiling C++. 898 if (!Types.getContext().getLangOptions().CPlusPlus) 899 return; 900 901 const Type *elementType = T->getBaseElementTypeUnsafe(); 902 903 if (const MemberPointerType *MPT = elementType->getAs<MemberPointerType>()) { 904 if (!Types.getCXXABI().isZeroInitializable(MPT)) 905 IsZeroInitializable = IsZeroInitializableAsBase = false; 906 } else if (const RecordType *RT = elementType->getAs<RecordType>()) { 907 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 908 const CGRecordLayout &Layout = Types.getCGRecordLayout(RD); 909 if (!Layout.isZeroInitializable()) 910 IsZeroInitializable = IsZeroInitializableAsBase = false; 911 } 912} 913 914CGRecordLayout *CodeGenTypes::ComputeRecordLayout(const RecordDecl *D) { 915 CGRecordLayoutBuilder Builder(*this); 916 917 Builder.Layout(D); 918 919 const llvm::StructType *Ty = llvm::StructType::get(getLLVMContext(), 920 Builder.FieldTypes, 921 Builder.Packed); 922 923 // If we're in C++, compute the base subobject type. 924 const llvm::StructType *BaseTy = 0; 925 if (isa<CXXRecordDecl>(D)) { 926 BaseTy = Builder.BaseSubobjectType; 927 if (!BaseTy) BaseTy = Ty; 928 } 929 930 CGRecordLayout *RL = 931 new CGRecordLayout(Ty, BaseTy, Builder.IsZeroInitializable, 932 Builder.IsZeroInitializableAsBase); 933 934 RL->NonVirtualBases.swap(Builder.NonVirtualBases); 935 RL->CompleteObjectVirtualBases.swap(Builder.VirtualBases); 936 937 // Add all the field numbers. 938 RL->FieldInfo.swap(Builder.Fields); 939 940 // Add bitfield info. 941 RL->BitFields.swap(Builder.BitFields); 942 943 // Dump the layout, if requested. 944 if (getContext().getLangOptions().DumpRecordLayouts) { 945 llvm::errs() << "\n*** Dumping IRgen Record Layout\n"; 946 llvm::errs() << "Record: "; 947 D->dump(); 948 llvm::errs() << "\nLayout: "; 949 RL->dump(); 950 } 951 952#ifndef NDEBUG 953 // Verify that the computed LLVM struct size matches the AST layout size. 954 const ASTRecordLayout &Layout = getContext().getASTRecordLayout(D); 955 956 uint64_t TypeSizeInBits = getContext().toBits(Layout.getSize()); 957 assert(TypeSizeInBits == getTargetData().getTypeAllocSizeInBits(Ty) && 958 "Type size mismatch!"); 959 960 if (BaseTy) { 961 CharUnits NonVirtualSize = Layout.getNonVirtualSize(); 962 CharUnits NonVirtualAlign = Layout.getNonVirtualAlign(); 963 CharUnits AlignedNonVirtualTypeSize = 964 NonVirtualSize.RoundUpToAlignment(NonVirtualAlign); 965 966 uint64_t AlignedNonVirtualTypeSizeInBits = 967 getContext().toBits(AlignedNonVirtualTypeSize); 968 969 assert(AlignedNonVirtualTypeSizeInBits == 970 getTargetData().getTypeAllocSizeInBits(BaseTy) && 971 "Type size mismatch!"); 972 } 973 974 // Verify that the LLVM and AST field offsets agree. 975 const llvm::StructType *ST = 976 dyn_cast<llvm::StructType>(RL->getLLVMType()); 977 const llvm::StructLayout *SL = getTargetData().getStructLayout(ST); 978 979 const ASTRecordLayout &AST_RL = getContext().getASTRecordLayout(D); 980 RecordDecl::field_iterator it = D->field_begin(); 981 const FieldDecl *LastFD = 0; 982 bool IsMsStruct = D->hasAttr<MsStructAttr>(); 983 for (unsigned i = 0, e = AST_RL.getFieldCount(); i != e; ++i, ++it) { 984 const FieldDecl *FD = *it; 985 986 // For non-bit-fields, just check that the LLVM struct offset matches the 987 // AST offset. 988 if (!FD->isBitField()) { 989 unsigned FieldNo = RL->getLLVMFieldNo(FD); 990 assert(AST_RL.getFieldOffset(i) == SL->getElementOffsetInBits(FieldNo) && 991 "Invalid field offset!"); 992 LastFD = FD; 993 continue; 994 } 995 996 if (IsMsStruct) { 997 // Zero-length bitfields following non-bitfield members are 998 // ignored: 999 if (getContext().ZeroBitfieldFollowsNonBitfield(FD, LastFD)) { 1000 --i; 1001 continue; 1002 } 1003 LastFD = FD; 1004 } 1005 1006 // Ignore unnamed bit-fields. 1007 if (!FD->getDeclName()) { 1008 LastFD = FD; 1009 continue; 1010 } 1011 1012 const CGBitFieldInfo &Info = RL->getBitFieldInfo(FD); 1013 for (unsigned i = 0, e = Info.getNumComponents(); i != e; ++i) { 1014 const CGBitFieldInfo::AccessInfo &AI = Info.getComponent(i); 1015 1016 // Verify that every component access is within the structure. 1017 uint64_t FieldOffset = SL->getElementOffsetInBits(AI.FieldIndex); 1018 uint64_t AccessBitOffset = FieldOffset + 1019 getContext().toBits(AI.FieldByteOffset); 1020 assert(AccessBitOffset + AI.AccessWidth <= TypeSizeInBits && 1021 "Invalid bit-field access (out of range)!"); 1022 } 1023 } 1024#endif 1025 1026 return RL; 1027} 1028 1029void CGRecordLayout::print(llvm::raw_ostream &OS) const { 1030 OS << "<CGRecordLayout\n"; 1031 OS << " LLVMType:" << *CompleteObjectType << "\n"; 1032 if (BaseSubobjectType) 1033 OS << " NonVirtualBaseLLVMType:" << *BaseSubobjectType << "\n"; 1034 OS << " IsZeroInitializable:" << IsZeroInitializable << "\n"; 1035 OS << " BitFields:[\n"; 1036 1037 // Print bit-field infos in declaration order. 1038 std::vector<std::pair<unsigned, const CGBitFieldInfo*> > BFIs; 1039 for (llvm::DenseMap<const FieldDecl*, CGBitFieldInfo>::const_iterator 1040 it = BitFields.begin(), ie = BitFields.end(); 1041 it != ie; ++it) { 1042 const RecordDecl *RD = it->first->getParent(); 1043 unsigned Index = 0; 1044 for (RecordDecl::field_iterator 1045 it2 = RD->field_begin(); *it2 != it->first; ++it2) 1046 ++Index; 1047 BFIs.push_back(std::make_pair(Index, &it->second)); 1048 } 1049 llvm::array_pod_sort(BFIs.begin(), BFIs.end()); 1050 for (unsigned i = 0, e = BFIs.size(); i != e; ++i) { 1051 OS.indent(4); 1052 BFIs[i].second->print(OS); 1053 OS << "\n"; 1054 } 1055 1056 OS << "]>\n"; 1057} 1058 1059void CGRecordLayout::dump() const { 1060 print(llvm::errs()); 1061} 1062 1063void CGBitFieldInfo::print(llvm::raw_ostream &OS) const { 1064 OS << "<CGBitFieldInfo"; 1065 OS << " Size:" << Size; 1066 OS << " IsSigned:" << IsSigned << "\n"; 1067 1068 OS.indent(4 + strlen("<CGBitFieldInfo")); 1069 OS << " NumComponents:" << getNumComponents(); 1070 OS << " Components: ["; 1071 if (getNumComponents()) { 1072 OS << "\n"; 1073 for (unsigned i = 0, e = getNumComponents(); i != e; ++i) { 1074 const AccessInfo &AI = getComponent(i); 1075 OS.indent(8); 1076 OS << "<AccessInfo" 1077 << " FieldIndex:" << AI.FieldIndex 1078 << " FieldByteOffset:" << AI.FieldByteOffset.getQuantity() 1079 << " FieldBitStart:" << AI.FieldBitStart 1080 << " AccessWidth:" << AI.AccessWidth << "\n"; 1081 OS.indent(8 + strlen("<AccessInfo")); 1082 OS << " AccessAlignment:" << AI.AccessAlignment.getQuantity() 1083 << " TargetBitOffset:" << AI.TargetBitOffset 1084 << " TargetBitWidth:" << AI.TargetBitWidth 1085 << ">\n"; 1086 } 1087 OS.indent(4); 1088 } 1089 OS << "]>"; 1090} 1091 1092void CGBitFieldInfo::dump() const { 1093 print(llvm::errs()); 1094} 1095