CGRecordLayoutBuilder.cpp revision 219077
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 std::vector<const llvm::Type *> 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 81private: 82 CodeGenTypes &Types; 83 84 /// Alignment - Contains the alignment of the RecordDecl. 85 // 86 // FIXME: This is not needed and should be removed. 87 CharUnits Alignment; 88 89 /// BitsAvailableInLastField - If a bit field spans only part of a LLVM field, 90 /// this will have the number of bits still available in the field. 91 char BitsAvailableInLastField; 92 93 /// NextFieldOffset - Holds the next field offset. 94 CharUnits NextFieldOffset; 95 96 /// LayoutUnionField - Will layout a field in an union and return the type 97 /// that the field will have. 98 const llvm::Type *LayoutUnionField(const FieldDecl *Field, 99 const ASTRecordLayout &Layout); 100 101 /// LayoutUnion - Will layout a union RecordDecl. 102 void LayoutUnion(const RecordDecl *D); 103 104 /// LayoutField - try to layout all fields in the record decl. 105 /// Returns false if the operation failed because the struct is not packed. 106 bool LayoutFields(const RecordDecl *D); 107 108 /// Layout a single base, virtual or non-virtual 109 void LayoutBase(const CXXRecordDecl *base, 110 const CGRecordLayout &baseLayout, 111 CharUnits baseOffset); 112 113 /// LayoutVirtualBase - layout a single virtual base. 114 void LayoutVirtualBase(const CXXRecordDecl *base, 115 CharUnits baseOffset); 116 117 /// LayoutVirtualBases - layout the virtual bases of a record decl. 118 void LayoutVirtualBases(const CXXRecordDecl *RD, 119 const ASTRecordLayout &Layout); 120 121 /// LayoutNonVirtualBase - layout a single non-virtual base. 122 void LayoutNonVirtualBase(const CXXRecordDecl *base, 123 CharUnits baseOffset); 124 125 /// LayoutNonVirtualBases - layout the virtual bases of a record decl. 126 void LayoutNonVirtualBases(const CXXRecordDecl *RD, 127 const ASTRecordLayout &Layout); 128 129 /// ComputeNonVirtualBaseType - Compute the non-virtual base field types. 130 bool ComputeNonVirtualBaseType(const CXXRecordDecl *RD); 131 132 /// LayoutField - layout a single field. Returns false if the operation failed 133 /// because the current struct is not packed. 134 bool LayoutField(const FieldDecl *D, uint64_t FieldOffset); 135 136 /// LayoutBitField - layout a single bit field. 137 void LayoutBitField(const FieldDecl *D, uint64_t FieldOffset); 138 139 /// AppendField - Appends a field with the given offset and type. 140 void AppendField(CharUnits fieldOffset, const llvm::Type *FieldTy); 141 142 /// AppendPadding - Appends enough padding bytes so that the total 143 /// struct size is a multiple of the field alignment. 144 void AppendPadding(CharUnits fieldOffset, CharUnits fieldAlignment); 145 146 /// getByteArrayType - Returns a byte array type with the given number of 147 /// elements. 148 const llvm::Type *getByteArrayType(CharUnits NumBytes); 149 150 /// AppendBytes - Append a given number of bytes to the record. 151 void AppendBytes(CharUnits numBytes); 152 153 /// AppendTailPadding - Append enough tail padding so that the type will have 154 /// the passed size. 155 void AppendTailPadding(uint64_t RecordSize); 156 157 CharUnits getTypeAlignment(const llvm::Type *Ty) const; 158 159 /// getAlignmentAsLLVMStruct - Returns the maximum alignment of all the 160 /// LLVM element types. 161 CharUnits getAlignmentAsLLVMStruct() const; 162 163 /// CheckZeroInitializable - Check if the given type contains a pointer 164 /// to data member. 165 void CheckZeroInitializable(QualType T); 166 167public: 168 CGRecordLayoutBuilder(CodeGenTypes &Types) 169 : BaseSubobjectType(0), 170 IsZeroInitializable(true), IsZeroInitializableAsBase(true), 171 Packed(false), Types(Types), BitsAvailableInLastField(0) { } 172 173 /// Layout - Will layout a RecordDecl. 174 void Layout(const RecordDecl *D); 175}; 176 177} 178 179void CGRecordLayoutBuilder::Layout(const RecordDecl *D) { 180 Alignment = Types.getContext().getASTRecordLayout(D).getAlignment(); 181 Packed = D->hasAttr<PackedAttr>(); 182 183 if (D->isUnion()) { 184 LayoutUnion(D); 185 return; 186 } 187 188 if (LayoutFields(D)) 189 return; 190 191 // We weren't able to layout the struct. Try again with a packed struct 192 Packed = true; 193 NextFieldOffset = CharUnits::Zero(); 194 FieldTypes.clear(); 195 Fields.clear(); 196 BitFields.clear(); 197 NonVirtualBases.clear(); 198 VirtualBases.clear(); 199 200 LayoutFields(D); 201} 202 203CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types, 204 const FieldDecl *FD, 205 uint64_t FieldOffset, 206 uint64_t FieldSize, 207 uint64_t ContainingTypeSizeInBits, 208 unsigned ContainingTypeAlign) { 209 const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(FD->getType()); 210 CharUnits TypeSizeInBytes = 211 CharUnits::fromQuantity(Types.getTargetData().getTypeAllocSize(Ty)); 212 uint64_t TypeSizeInBits = Types.getContext().toBits(TypeSizeInBytes); 213 214 bool IsSigned = FD->getType()->isSignedIntegerType(); 215 216 if (FieldSize > TypeSizeInBits) { 217 // We have a wide bit-field. The extra bits are only used for padding, so 218 // if we have a bitfield of type T, with size N: 219 // 220 // T t : N; 221 // 222 // We can just assume that it's: 223 // 224 // T t : sizeof(T); 225 // 226 FieldSize = TypeSizeInBits; 227 } 228 229 // in big-endian machines the first fields are in higher bit positions, 230 // so revert the offset. The byte offsets are reversed(back) later. 231 if (Types.getTargetData().isBigEndian()) { 232 FieldOffset = ((ContainingTypeSizeInBits)-FieldOffset-FieldSize); 233 } 234 235 // Compute the access components. The policy we use is to start by attempting 236 // to access using the width of the bit-field type itself and to always access 237 // at aligned indices of that type. If such an access would fail because it 238 // extends past the bound of the type, then we reduce size to the next smaller 239 // power of two and retry. The current algorithm assumes pow2 sized types, 240 // although this is easy to fix. 241 // 242 assert(llvm::isPowerOf2_32(TypeSizeInBits) && "Unexpected type size!"); 243 CGBitFieldInfo::AccessInfo Components[3]; 244 unsigned NumComponents = 0; 245 unsigned AccessedTargetBits = 0; // The tumber of target bits accessed. 246 unsigned AccessWidth = TypeSizeInBits; // The current access width to attempt. 247 248 // Round down from the field offset to find the first access position that is 249 // at an aligned offset of the initial access type. 250 uint64_t AccessStart = FieldOffset - (FieldOffset % AccessWidth); 251 252 // Adjust initial access size to fit within record. 253 while (AccessWidth > Types.getTarget().getCharWidth() && 254 AccessStart + AccessWidth > ContainingTypeSizeInBits) { 255 AccessWidth >>= 1; 256 AccessStart = FieldOffset - (FieldOffset % AccessWidth); 257 } 258 259 while (AccessedTargetBits < FieldSize) { 260 // Check that we can access using a type of this size, without reading off 261 // the end of the structure. This can occur with packed structures and 262 // -fno-bitfield-type-align, for example. 263 if (AccessStart + AccessWidth > ContainingTypeSizeInBits) { 264 // If so, reduce access size to the next smaller power-of-two and retry. 265 AccessWidth >>= 1; 266 assert(AccessWidth >= Types.getTarget().getCharWidth() 267 && "Cannot access under byte size!"); 268 continue; 269 } 270 271 // Otherwise, add an access component. 272 273 // First, compute the bits inside this access which are part of the 274 // target. We are reading bits [AccessStart, AccessStart + AccessWidth); the 275 // intersection with [FieldOffset, FieldOffset + FieldSize) gives the bits 276 // in the target that we are reading. 277 assert(FieldOffset < AccessStart + AccessWidth && "Invalid access start!"); 278 assert(AccessStart < FieldOffset + FieldSize && "Invalid access start!"); 279 uint64_t AccessBitsInFieldStart = std::max(AccessStart, FieldOffset); 280 uint64_t AccessBitsInFieldSize = 281 std::min(AccessWidth + AccessStart, 282 FieldOffset + FieldSize) - AccessBitsInFieldStart; 283 284 assert(NumComponents < 3 && "Unexpected number of components!"); 285 CGBitFieldInfo::AccessInfo &AI = Components[NumComponents++]; 286 AI.FieldIndex = 0; 287 // FIXME: We still follow the old access pattern of only using the field 288 // byte offset. We should switch this once we fix the struct layout to be 289 // pretty. 290 291 // on big-endian machines we reverted the bit offset because first fields are 292 // in higher bits. But this also reverts the bytes, so fix this here by reverting 293 // the byte offset on big-endian machines. 294 if (Types.getTargetData().isBigEndian()) { 295 AI.FieldByteOffset = (ContainingTypeSizeInBits - AccessStart - AccessWidth )/8; 296 } else { 297 AI.FieldByteOffset = AccessStart / 8; 298 } 299 AI.FieldBitStart = AccessBitsInFieldStart - AccessStart; 300 AI.AccessWidth = AccessWidth; 301 AI.AccessAlignment = llvm::MinAlign(ContainingTypeAlign, AccessStart) / 8; 302 AI.TargetBitOffset = AccessedTargetBits; 303 AI.TargetBitWidth = AccessBitsInFieldSize; 304 305 AccessStart += AccessWidth; 306 AccessedTargetBits += AI.TargetBitWidth; 307 } 308 309 assert(AccessedTargetBits == FieldSize && "Invalid bit-field access!"); 310 return CGBitFieldInfo(FieldSize, NumComponents, Components, IsSigned); 311} 312 313CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types, 314 const FieldDecl *FD, 315 uint64_t FieldOffset, 316 uint64_t FieldSize) { 317 const RecordDecl *RD = FD->getParent(); 318 const ASTRecordLayout &RL = Types.getContext().getASTRecordLayout(RD); 319 uint64_t ContainingTypeSizeInBits = Types.getContext().toBits(RL.getSize()); 320 unsigned ContainingTypeAlign = Types.getContext().toBits(RL.getAlignment()); 321 322 return MakeInfo(Types, FD, FieldOffset, FieldSize, ContainingTypeSizeInBits, 323 ContainingTypeAlign); 324} 325 326void CGRecordLayoutBuilder::LayoutBitField(const FieldDecl *D, 327 uint64_t fieldOffset) { 328 uint64_t fieldSize = 329 D->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue(); 330 331 if (fieldSize == 0) 332 return; 333 334 uint64_t nextFieldOffsetInBits = Types.getContext().toBits(NextFieldOffset); 335 unsigned numBytesToAppend; 336 337 if (fieldOffset < nextFieldOffsetInBits) { 338 assert(BitsAvailableInLastField && "Bitfield size mismatch!"); 339 assert(!NextFieldOffset.isZero() && "Must have laid out at least one byte"); 340 341 // The bitfield begins in the previous bit-field. 342 numBytesToAppend = 343 llvm::RoundUpToAlignment(fieldSize - BitsAvailableInLastField, 8) / 8; 344 } else { 345 assert(fieldOffset % 8 == 0 && "Field offset not aligned correctly"); 346 347 // Append padding if necessary. 348 AppendPadding(CharUnits::fromQuantity(fieldOffset / 8), CharUnits::One()); 349 350 numBytesToAppend = llvm::RoundUpToAlignment(fieldSize, 8) / 8; 351 352 assert(numBytesToAppend && "No bytes to append!"); 353 } 354 355 // Add the bit field info. 356 BitFields.insert(std::make_pair(D, 357 CGBitFieldInfo::MakeInfo(Types, D, fieldOffset, fieldSize))); 358 359 AppendBytes(CharUnits::fromQuantity(numBytesToAppend)); 360 361 BitsAvailableInLastField = 362 NextFieldOffset.getQuantity() * 8 - (fieldOffset + fieldSize); 363} 364 365bool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D, 366 uint64_t fieldOffset) { 367 // If the field is packed, then we need a packed struct. 368 if (!Packed && D->hasAttr<PackedAttr>()) 369 return false; 370 371 if (D->isBitField()) { 372 // We must use packed structs for unnamed bit fields since they 373 // don't affect the struct alignment. 374 if (!Packed && !D->getDeclName()) 375 return false; 376 377 LayoutBitField(D, fieldOffset); 378 return true; 379 } 380 381 CheckZeroInitializable(D->getType()); 382 383 assert(fieldOffset % Types.getTarget().getCharWidth() == 0 384 && "field offset is not on a byte boundary!"); 385 CharUnits fieldOffsetInBytes 386 = Types.getContext().toCharUnitsFromBits(fieldOffset); 387 388 const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(D->getType()); 389 CharUnits typeAlignment = getTypeAlignment(Ty); 390 391 // If the type alignment is larger then the struct alignment, we must use 392 // a packed struct. 393 if (typeAlignment > Alignment) { 394 assert(!Packed && "Alignment is wrong even with packed struct!"); 395 return false; 396 } 397 398 if (!Packed) { 399 if (const RecordType *RT = D->getType()->getAs<RecordType>()) { 400 const RecordDecl *RD = cast<RecordDecl>(RT->getDecl()); 401 if (const MaxFieldAlignmentAttr *MFAA = 402 RD->getAttr<MaxFieldAlignmentAttr>()) { 403 if (MFAA->getAlignment() != Types.getContext().toBits(typeAlignment)) 404 return false; 405 } 406 } 407 } 408 409 // Round up the field offset to the alignment of the field type. 410 CharUnits alignedNextFieldOffsetInBytes = 411 NextFieldOffset.RoundUpToAlignment(typeAlignment); 412 413 if (fieldOffsetInBytes < alignedNextFieldOffsetInBytes) { 414 assert(!Packed && "Could not place field even with packed struct!"); 415 return false; 416 } 417 418 AppendPadding(fieldOffsetInBytes, typeAlignment); 419 420 // Now append the field. 421 Fields[D] = FieldTypes.size(); 422 AppendField(fieldOffsetInBytes, Ty); 423 424 return true; 425} 426 427const llvm::Type * 428CGRecordLayoutBuilder::LayoutUnionField(const FieldDecl *Field, 429 const ASTRecordLayout &Layout) { 430 if (Field->isBitField()) { 431 uint64_t FieldSize = 432 Field->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue(); 433 434 // Ignore zero sized bit fields. 435 if (FieldSize == 0) 436 return 0; 437 438 const llvm::Type *FieldTy = llvm::Type::getInt8Ty(Types.getLLVMContext()); 439 unsigned NumBytesToAppend = 440 llvm::RoundUpToAlignment(FieldSize, 8) / 8; 441 442 if (NumBytesToAppend > 1) 443 FieldTy = llvm::ArrayType::get(FieldTy, NumBytesToAppend); 444 445 // Add the bit field info. 446 BitFields.insert(std::make_pair(Field, 447 CGBitFieldInfo::MakeInfo(Types, Field, 0, FieldSize))); 448 return FieldTy; 449 } 450 451 // This is a regular union field. 452 Fields[Field] = 0; 453 return Types.ConvertTypeForMemRecursive(Field->getType()); 454} 455 456void CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) { 457 assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!"); 458 459 const ASTRecordLayout &layout = Types.getContext().getASTRecordLayout(D); 460 461 const llvm::Type *unionType = 0; 462 CharUnits unionSize = CharUnits::Zero(); 463 CharUnits unionAlign = CharUnits::Zero(); 464 465 bool hasOnlyZeroSizedBitFields = true; 466 467 unsigned fieldNo = 0; 468 for (RecordDecl::field_iterator field = D->field_begin(), 469 fieldEnd = D->field_end(); field != fieldEnd; ++field, ++fieldNo) { 470 assert(layout.getFieldOffset(fieldNo) == 0 && 471 "Union field offset did not start at the beginning of record!"); 472 const llvm::Type *fieldType = LayoutUnionField(*field, layout); 473 474 if (!fieldType) 475 continue; 476 477 hasOnlyZeroSizedBitFields = false; 478 479 CharUnits fieldAlign = CharUnits::fromQuantity( 480 Types.getTargetData().getABITypeAlignment(fieldType)); 481 CharUnits fieldSize = CharUnits::fromQuantity( 482 Types.getTargetData().getTypeAllocSize(fieldType)); 483 484 if (fieldAlign < unionAlign) 485 continue; 486 487 if (fieldAlign > unionAlign || fieldSize > unionSize) { 488 unionType = fieldType; 489 unionAlign = fieldAlign; 490 unionSize = fieldSize; 491 } 492 } 493 494 // Now add our field. 495 if (unionType) { 496 AppendField(CharUnits::Zero(), unionType); 497 498 if (getTypeAlignment(unionType) > layout.getAlignment()) { 499 // We need a packed struct. 500 Packed = true; 501 unionAlign = CharUnits::One(); 502 } 503 } 504 if (unionAlign.isZero()) { 505 assert(hasOnlyZeroSizedBitFields && 506 "0-align record did not have all zero-sized bit-fields!"); 507 unionAlign = CharUnits::One(); 508 } 509 510 // Append tail padding. 511 CharUnits recordSize = layout.getSize(); 512 if (recordSize > unionSize) 513 AppendPadding(recordSize, unionAlign); 514} 515 516void CGRecordLayoutBuilder::LayoutBase(const CXXRecordDecl *base, 517 const CGRecordLayout &baseLayout, 518 CharUnits baseOffset) { 519 AppendPadding(baseOffset, CharUnits::One()); 520 521 const ASTRecordLayout &baseASTLayout 522 = Types.getContext().getASTRecordLayout(base); 523 524 // Fields and bases can be laid out in the tail padding of previous 525 // bases. If this happens, we need to allocate the base as an i8 526 // array; otherwise, we can use the subobject type. However, 527 // actually doing that would require knowledge of what immediately 528 // follows this base in the layout, so instead we do a conservative 529 // approximation, which is to use the base subobject type if it 530 // has the same LLVM storage size as the nvsize. 531 532 // The nvsize, i.e. the unpadded size of the base class. 533 CharUnits nvsize = baseASTLayout.getNonVirtualSize(); 534 535#if 0 536 const llvm::StructType *subobjectType = baseLayout.getBaseSubobjectLLVMType(); 537 const llvm::StructLayout *baseLLVMLayout = 538 Types.getTargetData().getStructLayout(subobjectType); 539 CharUnits stsize = CharUnits::fromQuantity(baseLLVMLayout->getSizeInBytes()); 540 541 if (nvsize == stsize) 542 AppendField(baseOffset, subobjectType); 543 else 544#endif 545 AppendBytes(nvsize); 546} 547 548void CGRecordLayoutBuilder::LayoutNonVirtualBase(const CXXRecordDecl *base, 549 CharUnits baseOffset) { 550 // Ignore empty bases. 551 if (base->isEmpty()) return; 552 553 const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base); 554 if (IsZeroInitializableAsBase) { 555 assert(IsZeroInitializable && 556 "class zero-initializable as base but not as complete object"); 557 558 IsZeroInitializable = IsZeroInitializableAsBase = 559 baseLayout.isZeroInitializableAsBase(); 560 } 561 562 LayoutBase(base, baseLayout, baseOffset); 563 NonVirtualBases[base] = (FieldTypes.size() - 1); 564} 565 566void 567CGRecordLayoutBuilder::LayoutVirtualBase(const CXXRecordDecl *base, 568 CharUnits baseOffset) { 569 // Ignore empty bases. 570 if (base->isEmpty()) return; 571 572 const CGRecordLayout &baseLayout = Types.getCGRecordLayout(base); 573 if (IsZeroInitializable) 574 IsZeroInitializable = baseLayout.isZeroInitializableAsBase(); 575 576 LayoutBase(base, baseLayout, baseOffset); 577 VirtualBases[base] = (FieldTypes.size() - 1); 578} 579 580/// LayoutVirtualBases - layout the non-virtual bases of a record decl. 581void 582CGRecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD, 583 const ASTRecordLayout &Layout) { 584 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 585 E = RD->bases_end(); I != E; ++I) { 586 const CXXRecordDecl *BaseDecl = 587 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 588 589 // We only want to lay out virtual bases that aren't indirect primary bases 590 // of some other base. 591 if (I->isVirtual() && !IndirectPrimaryBases.count(BaseDecl)) { 592 // Only lay out the base once. 593 if (!LaidOutVirtualBases.insert(BaseDecl)) 594 continue; 595 596 CharUnits vbaseOffset = Layout.getVBaseClassOffset(BaseDecl); 597 LayoutVirtualBase(BaseDecl, vbaseOffset); 598 } 599 600 if (!BaseDecl->getNumVBases()) { 601 // This base isn't interesting since it doesn't have any virtual bases. 602 continue; 603 } 604 605 LayoutVirtualBases(BaseDecl, Layout); 606 } 607} 608 609void 610CGRecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD, 611 const ASTRecordLayout &Layout) { 612 const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase(); 613 614 // Check if we need to add a vtable pointer. 615 if (RD->isDynamicClass()) { 616 if (!PrimaryBase) { 617 const llvm::Type *FunctionType = 618 llvm::FunctionType::get(llvm::Type::getInt32Ty(Types.getLLVMContext()), 619 /*isVarArg=*/true); 620 const llvm::Type *VTableTy = FunctionType->getPointerTo(); 621 622 assert(NextFieldOffset.isZero() && 623 "VTable pointer must come first!"); 624 AppendField(CharUnits::Zero(), VTableTy->getPointerTo()); 625 } else { 626 if (!Layout.isPrimaryBaseVirtual()) 627 LayoutNonVirtualBase(PrimaryBase, CharUnits::Zero()); 628 else 629 LayoutVirtualBase(PrimaryBase, CharUnits::Zero()); 630 } 631 } 632 633 // Layout the non-virtual bases. 634 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 635 E = RD->bases_end(); I != E; ++I) { 636 if (I->isVirtual()) 637 continue; 638 639 const CXXRecordDecl *BaseDecl = 640 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 641 642 // We've already laid out the primary base. 643 if (BaseDecl == PrimaryBase && !Layout.isPrimaryBaseVirtual()) 644 continue; 645 646 LayoutNonVirtualBase(BaseDecl, Layout.getBaseClassOffset(BaseDecl)); 647 } 648} 649 650bool 651CGRecordLayoutBuilder::ComputeNonVirtualBaseType(const CXXRecordDecl *RD) { 652 const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(RD); 653 654 CharUnits NonVirtualSize = Layout.getNonVirtualSize(); 655 CharUnits NonVirtualAlign = Layout.getNonVirtualAlign(); 656 CharUnits AlignedNonVirtualTypeSize = 657 NonVirtualSize.RoundUpToAlignment(NonVirtualAlign); 658 659 // First check if we can use the same fields as for the complete class. 660 CharUnits RecordSize = Layout.getSize(); 661 if (AlignedNonVirtualTypeSize == RecordSize) 662 return true; 663 664 // Check if we need padding. 665 CharUnits AlignedNextFieldOffset = 666 NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct()); 667 668 if (AlignedNextFieldOffset > AlignedNonVirtualTypeSize) { 669 assert(!Packed && "cannot layout even as packed struct"); 670 return false; // Needs packing. 671 } 672 673 bool needsPadding = (AlignedNonVirtualTypeSize != AlignedNextFieldOffset); 674 if (needsPadding) { 675 CharUnits NumBytes = AlignedNonVirtualTypeSize - AlignedNextFieldOffset; 676 FieldTypes.push_back(getByteArrayType(NumBytes)); 677 } 678 679 BaseSubobjectType = llvm::StructType::get(Types.getLLVMContext(), 680 FieldTypes, Packed); 681 682 if (needsPadding) { 683 // Pull the padding back off. 684 FieldTypes.pop_back(); 685 } 686 687 return true; 688} 689 690bool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) { 691 assert(!D->isUnion() && "Can't call LayoutFields on a union!"); 692 assert(!Alignment.isZero() && "Did not set alignment!"); 693 694 const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D); 695 696 const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D); 697 if (RD) 698 LayoutNonVirtualBases(RD, Layout); 699 700 unsigned FieldNo = 0; 701 702 for (RecordDecl::field_iterator Field = D->field_begin(), 703 FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 704 if (!LayoutField(*Field, Layout.getFieldOffset(FieldNo))) { 705 assert(!Packed && 706 "Could not layout fields even with a packed LLVM struct!"); 707 return false; 708 } 709 } 710 711 if (RD) { 712 // We've laid out the non-virtual bases and the fields, now compute the 713 // non-virtual base field types. 714 if (!ComputeNonVirtualBaseType(RD)) { 715 assert(!Packed && "Could not layout even with a packed LLVM struct!"); 716 return false; 717 } 718 719 // And lay out the virtual bases. 720 RD->getIndirectPrimaryBases(IndirectPrimaryBases); 721 if (Layout.isPrimaryBaseVirtual()) 722 IndirectPrimaryBases.insert(Layout.getPrimaryBase()); 723 LayoutVirtualBases(RD, Layout); 724 } 725 726 // Append tail padding if necessary. 727 AppendTailPadding(Types.getContext().toBits(Layout.getSize())); 728 729 return true; 730} 731 732void CGRecordLayoutBuilder::AppendTailPadding(uint64_t RecordSize) { 733 assert(RecordSize % 8 == 0 && "Invalid record size!"); 734 735 CharUnits RecordSizeInBytes = 736 Types.getContext().toCharUnitsFromBits(RecordSize); 737 assert(NextFieldOffset <= RecordSizeInBytes && "Size mismatch!"); 738 739 CharUnits AlignedNextFieldOffset = 740 NextFieldOffset.RoundUpToAlignment(getAlignmentAsLLVMStruct()); 741 742 if (AlignedNextFieldOffset == RecordSizeInBytes) { 743 // We don't need any padding. 744 return; 745 } 746 747 CharUnits NumPadBytes = RecordSizeInBytes - NextFieldOffset; 748 AppendBytes(NumPadBytes); 749} 750 751void CGRecordLayoutBuilder::AppendField(CharUnits fieldOffset, 752 const llvm::Type *fieldType) { 753 CharUnits fieldSize = 754 CharUnits::fromQuantity(Types.getTargetData().getTypeAllocSize(fieldType)); 755 756 FieldTypes.push_back(fieldType); 757 758 NextFieldOffset = fieldOffset + fieldSize; 759 BitsAvailableInLastField = 0; 760} 761 762void CGRecordLayoutBuilder::AppendPadding(CharUnits fieldOffset, 763 CharUnits fieldAlignment) { 764 assert(NextFieldOffset <= fieldOffset && 765 "Incorrect field layout!"); 766 767 // Round up the field offset to the alignment of the field type. 768 CharUnits alignedNextFieldOffset = 769 NextFieldOffset.RoundUpToAlignment(fieldAlignment); 770 771 if (alignedNextFieldOffset < fieldOffset) { 772 // Even with alignment, the field offset is not at the right place, 773 // insert padding. 774 CharUnits padding = fieldOffset - NextFieldOffset; 775 776 AppendBytes(padding); 777 } 778} 779 780const llvm::Type *CGRecordLayoutBuilder::getByteArrayType(CharUnits numBytes) { 781 assert(!numBytes.isZero() && "Empty byte arrays aren't allowed."); 782 783 const llvm::Type *Ty = llvm::Type::getInt8Ty(Types.getLLVMContext()); 784 if (numBytes > CharUnits::One()) 785 Ty = llvm::ArrayType::get(Ty, numBytes.getQuantity()); 786 787 return Ty; 788} 789 790void CGRecordLayoutBuilder::AppendBytes(CharUnits numBytes) { 791 if (numBytes.isZero()) 792 return; 793 794 // Append the padding field 795 AppendField(NextFieldOffset, getByteArrayType(numBytes)); 796} 797 798CharUnits CGRecordLayoutBuilder::getTypeAlignment(const llvm::Type *Ty) const { 799 if (Packed) 800 return CharUnits::One(); 801 802 return CharUnits::fromQuantity(Types.getTargetData().getABITypeAlignment(Ty)); 803} 804 805CharUnits CGRecordLayoutBuilder::getAlignmentAsLLVMStruct() const { 806 if (Packed) 807 return CharUnits::One(); 808 809 CharUnits maxAlignment = CharUnits::One(); 810 for (size_t i = 0; i != FieldTypes.size(); ++i) 811 maxAlignment = std::max(maxAlignment, getTypeAlignment(FieldTypes[i])); 812 813 return maxAlignment; 814} 815 816/// Merge in whether a field of the given type is zero-initializable. 817void CGRecordLayoutBuilder::CheckZeroInitializable(QualType T) { 818 // This record already contains a member pointer. 819 if (!IsZeroInitializableAsBase) 820 return; 821 822 // Can only have member pointers if we're compiling C++. 823 if (!Types.getContext().getLangOptions().CPlusPlus) 824 return; 825 826 const Type *elementType = T->getBaseElementTypeUnsafe(); 827 828 if (const MemberPointerType *MPT = elementType->getAs<MemberPointerType>()) { 829 if (!Types.getCXXABI().isZeroInitializable(MPT)) 830 IsZeroInitializable = IsZeroInitializableAsBase = false; 831 } else if (const RecordType *RT = elementType->getAs<RecordType>()) { 832 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 833 const CGRecordLayout &Layout = Types.getCGRecordLayout(RD); 834 if (!Layout.isZeroInitializable()) 835 IsZeroInitializable = IsZeroInitializableAsBase = false; 836 } 837} 838 839CGRecordLayout *CodeGenTypes::ComputeRecordLayout(const RecordDecl *D) { 840 CGRecordLayoutBuilder Builder(*this); 841 842 Builder.Layout(D); 843 844 const llvm::StructType *Ty = llvm::StructType::get(getLLVMContext(), 845 Builder.FieldTypes, 846 Builder.Packed); 847 848 // If we're in C++, compute the base subobject type. 849 const llvm::StructType *BaseTy = 0; 850 if (isa<CXXRecordDecl>(D)) { 851 BaseTy = Builder.BaseSubobjectType; 852 if (!BaseTy) BaseTy = Ty; 853 } 854 855 CGRecordLayout *RL = 856 new CGRecordLayout(Ty, BaseTy, Builder.IsZeroInitializable, 857 Builder.IsZeroInitializableAsBase); 858 859 RL->NonVirtualBases.swap(Builder.NonVirtualBases); 860 RL->CompleteObjectVirtualBases.swap(Builder.VirtualBases); 861 862 // Add all the field numbers. 863 RL->FieldInfo.swap(Builder.Fields); 864 865 // Add bitfield info. 866 RL->BitFields.swap(Builder.BitFields); 867 868 // Dump the layout, if requested. 869 if (getContext().getLangOptions().DumpRecordLayouts) { 870 llvm::errs() << "\n*** Dumping IRgen Record Layout\n"; 871 llvm::errs() << "Record: "; 872 D->dump(); 873 llvm::errs() << "\nLayout: "; 874 RL->dump(); 875 } 876 877#ifndef NDEBUG 878 // Verify that the computed LLVM struct size matches the AST layout size. 879 const ASTRecordLayout &Layout = getContext().getASTRecordLayout(D); 880 881 uint64_t TypeSizeInBits = getContext().toBits(Layout.getSize()); 882 assert(TypeSizeInBits == getTargetData().getTypeAllocSizeInBits(Ty) && 883 "Type size mismatch!"); 884 885 if (BaseTy) { 886 CharUnits NonVirtualSize = Layout.getNonVirtualSize(); 887 CharUnits NonVirtualAlign = Layout.getNonVirtualAlign(); 888 CharUnits AlignedNonVirtualTypeSize = 889 NonVirtualSize.RoundUpToAlignment(NonVirtualAlign); 890 891 uint64_t AlignedNonVirtualTypeSizeInBits = 892 getContext().toBits(AlignedNonVirtualTypeSize); 893 894 assert(AlignedNonVirtualTypeSizeInBits == 895 getTargetData().getTypeAllocSizeInBits(BaseTy) && 896 "Type size mismatch!"); 897 } 898 899 // Verify that the LLVM and AST field offsets agree. 900 const llvm::StructType *ST = 901 dyn_cast<llvm::StructType>(RL->getLLVMType()); 902 const llvm::StructLayout *SL = getTargetData().getStructLayout(ST); 903 904 const ASTRecordLayout &AST_RL = getContext().getASTRecordLayout(D); 905 RecordDecl::field_iterator it = D->field_begin(); 906 for (unsigned i = 0, e = AST_RL.getFieldCount(); i != e; ++i, ++it) { 907 const FieldDecl *FD = *it; 908 909 // For non-bit-fields, just check that the LLVM struct offset matches the 910 // AST offset. 911 if (!FD->isBitField()) { 912 unsigned FieldNo = RL->getLLVMFieldNo(FD); 913 assert(AST_RL.getFieldOffset(i) == SL->getElementOffsetInBits(FieldNo) && 914 "Invalid field offset!"); 915 continue; 916 } 917 918 // Ignore unnamed bit-fields. 919 if (!FD->getDeclName()) 920 continue; 921 922 const CGBitFieldInfo &Info = RL->getBitFieldInfo(FD); 923 for (unsigned i = 0, e = Info.getNumComponents(); i != e; ++i) { 924 const CGBitFieldInfo::AccessInfo &AI = Info.getComponent(i); 925 926 // Verify that every component access is within the structure. 927 uint64_t FieldOffset = SL->getElementOffsetInBits(AI.FieldIndex); 928 uint64_t AccessBitOffset = FieldOffset + 929 getContext().toBits(CharUnits::fromQuantity(AI.FieldByteOffset)); 930 assert(AccessBitOffset + AI.AccessWidth <= TypeSizeInBits && 931 "Invalid bit-field access (out of range)!"); 932 } 933 } 934#endif 935 936 return RL; 937} 938 939void CGRecordLayout::print(llvm::raw_ostream &OS) const { 940 OS << "<CGRecordLayout\n"; 941 OS << " LLVMType:" << *CompleteObjectType << "\n"; 942 if (BaseSubobjectType) 943 OS << " NonVirtualBaseLLVMType:" << *BaseSubobjectType << "\n"; 944 OS << " IsZeroInitializable:" << IsZeroInitializable << "\n"; 945 OS << " BitFields:[\n"; 946 947 // Print bit-field infos in declaration order. 948 std::vector<std::pair<unsigned, const CGBitFieldInfo*> > BFIs; 949 for (llvm::DenseMap<const FieldDecl*, CGBitFieldInfo>::const_iterator 950 it = BitFields.begin(), ie = BitFields.end(); 951 it != ie; ++it) { 952 const RecordDecl *RD = it->first->getParent(); 953 unsigned Index = 0; 954 for (RecordDecl::field_iterator 955 it2 = RD->field_begin(); *it2 != it->first; ++it2) 956 ++Index; 957 BFIs.push_back(std::make_pair(Index, &it->second)); 958 } 959 llvm::array_pod_sort(BFIs.begin(), BFIs.end()); 960 for (unsigned i = 0, e = BFIs.size(); i != e; ++i) { 961 OS.indent(4); 962 BFIs[i].second->print(OS); 963 OS << "\n"; 964 } 965 966 OS << "]>\n"; 967} 968 969void CGRecordLayout::dump() const { 970 print(llvm::errs()); 971} 972 973void CGBitFieldInfo::print(llvm::raw_ostream &OS) const { 974 OS << "<CGBitFieldInfo"; 975 OS << " Size:" << Size; 976 OS << " IsSigned:" << IsSigned << "\n"; 977 978 OS.indent(4 + strlen("<CGBitFieldInfo")); 979 OS << " NumComponents:" << getNumComponents(); 980 OS << " Components: ["; 981 if (getNumComponents()) { 982 OS << "\n"; 983 for (unsigned i = 0, e = getNumComponents(); i != e; ++i) { 984 const AccessInfo &AI = getComponent(i); 985 OS.indent(8); 986 OS << "<AccessInfo" 987 << " FieldIndex:" << AI.FieldIndex 988 << " FieldByteOffset:" << AI.FieldByteOffset 989 << " FieldBitStart:" << AI.FieldBitStart 990 << " AccessWidth:" << AI.AccessWidth << "\n"; 991 OS.indent(8 + strlen("<AccessInfo")); 992 OS << " AccessAlignment:" << AI.AccessAlignment 993 << " TargetBitOffset:" << AI.TargetBitOffset 994 << " TargetBitWidth:" << AI.TargetBitWidth 995 << ">\n"; 996 } 997 OS.indent(4); 998 } 999 OS << "]>"; 1000} 1001 1002void CGBitFieldInfo::dump() const { 1003 print(llvm::errs()); 1004} 1005