1 //===--- VTableBuilder.cpp - C++ vtable layout builder --------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This contains code dealing with generation of the layout of virtual tables.
12 //===----------------------------------------------------------------------===//
14 #include "clang/AST/VTableBuilder.h"
15 #include "clang/AST/ASTContext.h"
16 #include "clang/AST/ASTDiagnostic.h"
17 #include "clang/AST/CXXInheritance.h"
18 #include "clang/AST/RecordLayout.h"
19 #include "clang/Basic/TargetInfo.h"
20 #include "llvm/ADT/SetOperations.h"
21 #include "llvm/ADT/SmallPtrSet.h"
22 #include "llvm/Support/Format.h"
23 #include "llvm/Support/raw_ostream.h"
27 using namespace clang;
29 #define DUMP_OVERRIDERS 0
33 /// BaseOffset - Represents an offset from a derived class to a direct or
34 /// indirect base class.
36 /// DerivedClass - The derived class.
37 const CXXRecordDecl *DerivedClass;
39 /// VirtualBase - If the path from the derived class to the base class
40 /// involves virtual base classes, this holds the declaration of the last
41 /// virtual base in this path (i.e. closest to the base class).
42 const CXXRecordDecl *VirtualBase;
44 /// NonVirtualOffset - The offset from the derived class to the base class.
45 /// (Or the offset from the virtual base class to the base class, if the
46 /// path from the derived class to the base class involves a virtual base
48 CharUnits NonVirtualOffset;
50 BaseOffset() : DerivedClass(nullptr), VirtualBase(nullptr),
51 NonVirtualOffset(CharUnits::Zero()) { }
52 BaseOffset(const CXXRecordDecl *DerivedClass,
53 const CXXRecordDecl *VirtualBase, CharUnits NonVirtualOffset)
54 : DerivedClass(DerivedClass), VirtualBase(VirtualBase),
55 NonVirtualOffset(NonVirtualOffset) { }
57 bool isEmpty() const { return NonVirtualOffset.isZero() && !VirtualBase; }
60 /// FinalOverriders - Contains the final overrider member functions for all
61 /// member functions in the base subobjects of a class.
62 class FinalOverriders {
64 /// OverriderInfo - Information about a final overrider.
65 struct OverriderInfo {
66 /// Method - The method decl of the overrider.
67 const CXXMethodDecl *Method;
69 /// VirtualBase - The virtual base class subobject of this overrider.
70 /// Note that this records the closest derived virtual base class subobject.
71 const CXXRecordDecl *VirtualBase;
73 /// Offset - the base offset of the overrider's parent in the layout class.
76 OverriderInfo() : Method(nullptr), VirtualBase(nullptr),
77 Offset(CharUnits::Zero()) { }
81 /// MostDerivedClass - The most derived class for which the final overriders
83 const CXXRecordDecl *MostDerivedClass;
85 /// MostDerivedClassOffset - If we're building final overriders for a
86 /// construction vtable, this holds the offset from the layout class to the
87 /// most derived class.
88 const CharUnits MostDerivedClassOffset;
90 /// LayoutClass - The class we're using for layout information. Will be
91 /// different than the most derived class if the final overriders are for a
92 /// construction vtable.
93 const CXXRecordDecl *LayoutClass;
97 /// MostDerivedClassLayout - the AST record layout of the most derived class.
98 const ASTRecordLayout &MostDerivedClassLayout;
100 /// MethodBaseOffsetPairTy - Uniquely identifies a member function
101 /// in a base subobject.
102 typedef std::pair<const CXXMethodDecl *, CharUnits> MethodBaseOffsetPairTy;
104 typedef llvm::DenseMap<MethodBaseOffsetPairTy,
105 OverriderInfo> OverridersMapTy;
107 /// OverridersMap - The final overriders for all virtual member functions of
108 /// all the base subobjects of the most derived class.
109 OverridersMapTy OverridersMap;
111 /// SubobjectsToOffsetsMapTy - A mapping from a base subobject (represented
112 /// as a record decl and a subobject number) and its offsets in the most
113 /// derived class as well as the layout class.
114 typedef llvm::DenseMap<std::pair<const CXXRecordDecl *, unsigned>,
115 CharUnits> SubobjectOffsetMapTy;
117 typedef llvm::DenseMap<const CXXRecordDecl *, unsigned> SubobjectCountMapTy;
119 /// ComputeBaseOffsets - Compute the offsets for all base subobjects of the
121 void ComputeBaseOffsets(BaseSubobject Base, bool IsVirtual,
122 CharUnits OffsetInLayoutClass,
123 SubobjectOffsetMapTy &SubobjectOffsets,
124 SubobjectOffsetMapTy &SubobjectLayoutClassOffsets,
125 SubobjectCountMapTy &SubobjectCounts);
127 typedef llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedVirtualBasesSetTy;
129 /// dump - dump the final overriders for a base subobject, and all its direct
130 /// and indirect base subobjects.
131 void dump(raw_ostream &Out, BaseSubobject Base,
132 VisitedVirtualBasesSetTy& VisitedVirtualBases);
135 FinalOverriders(const CXXRecordDecl *MostDerivedClass,
136 CharUnits MostDerivedClassOffset,
137 const CXXRecordDecl *LayoutClass);
139 /// getOverrider - Get the final overrider for the given method declaration in
140 /// the subobject with the given base offset.
141 OverriderInfo getOverrider(const CXXMethodDecl *MD,
142 CharUnits BaseOffset) const {
143 assert(OverridersMap.count(std::make_pair(MD, BaseOffset)) &&
144 "Did not find overrider!");
146 return OverridersMap.lookup(std::make_pair(MD, BaseOffset));
149 /// dump - dump the final overriders.
151 VisitedVirtualBasesSetTy VisitedVirtualBases;
152 dump(llvm::errs(), BaseSubobject(MostDerivedClass, CharUnits::Zero()),
153 VisitedVirtualBases);
158 FinalOverriders::FinalOverriders(const CXXRecordDecl *MostDerivedClass,
159 CharUnits MostDerivedClassOffset,
160 const CXXRecordDecl *LayoutClass)
161 : MostDerivedClass(MostDerivedClass),
162 MostDerivedClassOffset(MostDerivedClassOffset), LayoutClass(LayoutClass),
163 Context(MostDerivedClass->getASTContext()),
164 MostDerivedClassLayout(Context.getASTRecordLayout(MostDerivedClass)) {
166 // Compute base offsets.
167 SubobjectOffsetMapTy SubobjectOffsets;
168 SubobjectOffsetMapTy SubobjectLayoutClassOffsets;
169 SubobjectCountMapTy SubobjectCounts;
170 ComputeBaseOffsets(BaseSubobject(MostDerivedClass, CharUnits::Zero()),
172 MostDerivedClassOffset,
173 SubobjectOffsets, SubobjectLayoutClassOffsets,
176 // Get the final overriders.
177 CXXFinalOverriderMap FinalOverriders;
178 MostDerivedClass->getFinalOverriders(FinalOverriders);
180 for (const auto &Overrider : FinalOverriders) {
181 const CXXMethodDecl *MD = Overrider.first;
182 const OverridingMethods &Methods = Overrider.second;
184 for (const auto &M : Methods) {
185 unsigned SubobjectNumber = M.first;
186 assert(SubobjectOffsets.count(std::make_pair(MD->getParent(),
188 "Did not find subobject offset!");
190 CharUnits BaseOffset = SubobjectOffsets[std::make_pair(MD->getParent(),
193 assert(M.second.size() == 1 && "Final overrider is not unique!");
194 const UniqueVirtualMethod &Method = M.second.front();
196 const CXXRecordDecl *OverriderRD = Method.Method->getParent();
197 assert(SubobjectLayoutClassOffsets.count(
198 std::make_pair(OverriderRD, Method.Subobject))
199 && "Did not find subobject offset!");
200 CharUnits OverriderOffset =
201 SubobjectLayoutClassOffsets[std::make_pair(OverriderRD,
204 OverriderInfo& Overrider = OverridersMap[std::make_pair(MD, BaseOffset)];
205 assert(!Overrider.Method && "Overrider should not exist yet!");
207 Overrider.Offset = OverriderOffset;
208 Overrider.Method = Method.Method;
209 Overrider.VirtualBase = Method.InVirtualSubobject;
214 // And dump them (for now).
219 static BaseOffset ComputeBaseOffset(const ASTContext &Context,
220 const CXXRecordDecl *DerivedRD,
221 const CXXBasePath &Path) {
222 CharUnits NonVirtualOffset = CharUnits::Zero();
224 unsigned NonVirtualStart = 0;
225 const CXXRecordDecl *VirtualBase = nullptr;
227 // First, look for the virtual base class.
228 for (int I = Path.size(), E = 0; I != E; --I) {
229 const CXXBasePathElement &Element = Path[I - 1];
231 if (Element.Base->isVirtual()) {
233 QualType VBaseType = Element.Base->getType();
234 VirtualBase = VBaseType->getAsCXXRecordDecl();
239 // Now compute the non-virtual offset.
240 for (unsigned I = NonVirtualStart, E = Path.size(); I != E; ++I) {
241 const CXXBasePathElement &Element = Path[I];
243 // Check the base class offset.
244 const ASTRecordLayout &Layout = Context.getASTRecordLayout(Element.Class);
246 const CXXRecordDecl *Base = Element.Base->getType()->getAsCXXRecordDecl();
248 NonVirtualOffset += Layout.getBaseClassOffset(Base);
251 // FIXME: This should probably use CharUnits or something. Maybe we should
252 // even change the base offsets in ASTRecordLayout to be specified in
254 return BaseOffset(DerivedRD, VirtualBase, NonVirtualOffset);
258 static BaseOffset ComputeBaseOffset(const ASTContext &Context,
259 const CXXRecordDecl *BaseRD,
260 const CXXRecordDecl *DerivedRD) {
261 CXXBasePaths Paths(/*FindAmbiguities=*/false,
262 /*RecordPaths=*/true, /*DetectVirtual=*/false);
264 if (!DerivedRD->isDerivedFrom(BaseRD, Paths))
265 llvm_unreachable("Class must be derived from the passed in base class!");
267 return ComputeBaseOffset(Context, DerivedRD, Paths.front());
271 ComputeReturnAdjustmentBaseOffset(ASTContext &Context,
272 const CXXMethodDecl *DerivedMD,
273 const CXXMethodDecl *BaseMD) {
274 const FunctionType *BaseFT = BaseMD->getType()->getAs<FunctionType>();
275 const FunctionType *DerivedFT = DerivedMD->getType()->getAs<FunctionType>();
277 // Canonicalize the return types.
278 CanQualType CanDerivedReturnType =
279 Context.getCanonicalType(DerivedFT->getReturnType());
280 CanQualType CanBaseReturnType =
281 Context.getCanonicalType(BaseFT->getReturnType());
283 assert(CanDerivedReturnType->getTypeClass() ==
284 CanBaseReturnType->getTypeClass() &&
285 "Types must have same type class!");
287 if (CanDerivedReturnType == CanBaseReturnType) {
288 // No adjustment needed.
292 if (isa<ReferenceType>(CanDerivedReturnType)) {
293 CanDerivedReturnType =
294 CanDerivedReturnType->getAs<ReferenceType>()->getPointeeType();
296 CanBaseReturnType->getAs<ReferenceType>()->getPointeeType();
297 } else if (isa<PointerType>(CanDerivedReturnType)) {
298 CanDerivedReturnType =
299 CanDerivedReturnType->getAs<PointerType>()->getPointeeType();
301 CanBaseReturnType->getAs<PointerType>()->getPointeeType();
303 llvm_unreachable("Unexpected return type!");
306 // We need to compare unqualified types here; consider
307 // const T *Base::foo();
308 // T *Derived::foo();
309 if (CanDerivedReturnType.getUnqualifiedType() ==
310 CanBaseReturnType.getUnqualifiedType()) {
311 // No adjustment needed.
315 const CXXRecordDecl *DerivedRD =
316 cast<CXXRecordDecl>(cast<RecordType>(CanDerivedReturnType)->getDecl());
318 const CXXRecordDecl *BaseRD =
319 cast<CXXRecordDecl>(cast<RecordType>(CanBaseReturnType)->getDecl());
321 return ComputeBaseOffset(Context, BaseRD, DerivedRD);
325 FinalOverriders::ComputeBaseOffsets(BaseSubobject Base, bool IsVirtual,
326 CharUnits OffsetInLayoutClass,
327 SubobjectOffsetMapTy &SubobjectOffsets,
328 SubobjectOffsetMapTy &SubobjectLayoutClassOffsets,
329 SubobjectCountMapTy &SubobjectCounts) {
330 const CXXRecordDecl *RD = Base.getBase();
332 unsigned SubobjectNumber = 0;
334 SubobjectNumber = ++SubobjectCounts[RD];
336 // Set up the subobject to offset mapping.
337 assert(!SubobjectOffsets.count(std::make_pair(RD, SubobjectNumber))
338 && "Subobject offset already exists!");
339 assert(!SubobjectLayoutClassOffsets.count(std::make_pair(RD, SubobjectNumber))
340 && "Subobject offset already exists!");
342 SubobjectOffsets[std::make_pair(RD, SubobjectNumber)] = Base.getBaseOffset();
343 SubobjectLayoutClassOffsets[std::make_pair(RD, SubobjectNumber)] =
346 // Traverse our bases.
347 for (const auto &B : RD->bases()) {
348 const CXXRecordDecl *BaseDecl = B.getType()->getAsCXXRecordDecl();
350 CharUnits BaseOffset;
351 CharUnits BaseOffsetInLayoutClass;
353 // Check if we've visited this virtual base before.
354 if (SubobjectOffsets.count(std::make_pair(BaseDecl, 0)))
357 const ASTRecordLayout &LayoutClassLayout =
358 Context.getASTRecordLayout(LayoutClass);
360 BaseOffset = MostDerivedClassLayout.getVBaseClassOffset(BaseDecl);
361 BaseOffsetInLayoutClass =
362 LayoutClassLayout.getVBaseClassOffset(BaseDecl);
364 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
365 CharUnits Offset = Layout.getBaseClassOffset(BaseDecl);
367 BaseOffset = Base.getBaseOffset() + Offset;
368 BaseOffsetInLayoutClass = OffsetInLayoutClass + Offset;
371 ComputeBaseOffsets(BaseSubobject(BaseDecl, BaseOffset),
372 B.isVirtual(), BaseOffsetInLayoutClass,
373 SubobjectOffsets, SubobjectLayoutClassOffsets,
378 void FinalOverriders::dump(raw_ostream &Out, BaseSubobject Base,
379 VisitedVirtualBasesSetTy &VisitedVirtualBases) {
380 const CXXRecordDecl *RD = Base.getBase();
381 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
383 for (const auto &B : RD->bases()) {
384 const CXXRecordDecl *BaseDecl = B.getType()->getAsCXXRecordDecl();
386 // Ignore bases that don't have any virtual member functions.
387 if (!BaseDecl->isPolymorphic())
390 CharUnits BaseOffset;
392 if (!VisitedVirtualBases.insert(BaseDecl).second) {
393 // We've visited this base before.
397 BaseOffset = MostDerivedClassLayout.getVBaseClassOffset(BaseDecl);
399 BaseOffset = Layout.getBaseClassOffset(BaseDecl) + Base.getBaseOffset();
402 dump(Out, BaseSubobject(BaseDecl, BaseOffset), VisitedVirtualBases);
405 Out << "Final overriders for (";
406 RD->printQualifiedName(Out);
408 Out << Base.getBaseOffset().getQuantity() << ")\n";
410 // Now dump the overriders for this base subobject.
411 for (const auto *MD : RD->methods()) {
412 if (!MD->isVirtual())
414 MD = MD->getCanonicalDecl();
416 OverriderInfo Overrider = getOverrider(MD, Base.getBaseOffset());
419 MD->printQualifiedName(Out);
421 Overrider.Method->printQualifiedName(Out);
422 Out << ", " << Overrider.Offset.getQuantity() << ')';
425 if (!Overrider.Method->isPure())
426 Offset = ComputeReturnAdjustmentBaseOffset(Context, Overrider.Method, MD);
428 if (!Offset.isEmpty()) {
429 Out << " [ret-adj: ";
430 if (Offset.VirtualBase) {
431 Offset.VirtualBase->printQualifiedName(Out);
435 Out << Offset.NonVirtualOffset.getQuantity() << " nv]";
442 /// VCallOffsetMap - Keeps track of vcall offsets when building a vtable.
443 struct VCallOffsetMap {
445 typedef std::pair<const CXXMethodDecl *, CharUnits> MethodAndOffsetPairTy;
447 /// Offsets - Keeps track of methods and their offsets.
448 // FIXME: This should be a real map and not a vector.
449 SmallVector<MethodAndOffsetPairTy, 16> Offsets;
451 /// MethodsCanShareVCallOffset - Returns whether two virtual member functions
452 /// can share the same vcall offset.
453 static bool MethodsCanShareVCallOffset(const CXXMethodDecl *LHS,
454 const CXXMethodDecl *RHS);
457 /// AddVCallOffset - Adds a vcall offset to the map. Returns true if the
458 /// add was successful, or false if there was already a member function with
459 /// the same signature in the map.
460 bool AddVCallOffset(const CXXMethodDecl *MD, CharUnits OffsetOffset);
462 /// getVCallOffsetOffset - Returns the vcall offset offset (relative to the
463 /// vtable address point) for the given virtual member function.
464 CharUnits getVCallOffsetOffset(const CXXMethodDecl *MD);
466 // empty - Return whether the offset map is empty or not.
467 bool empty() const { return Offsets.empty(); }
470 static bool HasSameVirtualSignature(const CXXMethodDecl *LHS,
471 const CXXMethodDecl *RHS) {
472 const FunctionProtoType *LT =
473 cast<FunctionProtoType>(LHS->getType().getCanonicalType());
474 const FunctionProtoType *RT =
475 cast<FunctionProtoType>(RHS->getType().getCanonicalType());
477 // Fast-path matches in the canonical types.
478 if (LT == RT) return true;
480 // Force the signatures to match. We can't rely on the overrides
481 // list here because there isn't necessarily an inheritance
482 // relationship between the two methods.
483 if (LT->getTypeQuals() != RT->getTypeQuals())
485 return LT->getParamTypes() == RT->getParamTypes();
488 bool VCallOffsetMap::MethodsCanShareVCallOffset(const CXXMethodDecl *LHS,
489 const CXXMethodDecl *RHS) {
490 assert(LHS->isVirtual() && "LHS must be virtual!");
491 assert(RHS->isVirtual() && "LHS must be virtual!");
493 // A destructor can share a vcall offset with another destructor.
494 if (isa<CXXDestructorDecl>(LHS))
495 return isa<CXXDestructorDecl>(RHS);
497 // FIXME: We need to check more things here.
499 // The methods must have the same name.
500 DeclarationName LHSName = LHS->getDeclName();
501 DeclarationName RHSName = RHS->getDeclName();
502 if (LHSName != RHSName)
505 // And the same signatures.
506 return HasSameVirtualSignature(LHS, RHS);
509 bool VCallOffsetMap::AddVCallOffset(const CXXMethodDecl *MD,
510 CharUnits OffsetOffset) {
511 // Check if we can reuse an offset.
512 for (const auto &OffsetPair : Offsets) {
513 if (MethodsCanShareVCallOffset(OffsetPair.first, MD))
518 Offsets.push_back(MethodAndOffsetPairTy(MD, OffsetOffset));
522 CharUnits VCallOffsetMap::getVCallOffsetOffset(const CXXMethodDecl *MD) {
523 // Look for an offset.
524 for (const auto &OffsetPair : Offsets) {
525 if (MethodsCanShareVCallOffset(OffsetPair.first, MD))
526 return OffsetPair.second;
529 llvm_unreachable("Should always find a vcall offset offset!");
532 /// VCallAndVBaseOffsetBuilder - Class for building vcall and vbase offsets.
533 class VCallAndVBaseOffsetBuilder {
535 typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits>
536 VBaseOffsetOffsetsMapTy;
539 /// MostDerivedClass - The most derived class for which we're building vcall
540 /// and vbase offsets.
541 const CXXRecordDecl *MostDerivedClass;
543 /// LayoutClass - The class we're using for layout information. Will be
544 /// different than the most derived class if we're building a construction
546 const CXXRecordDecl *LayoutClass;
548 /// Context - The ASTContext which we will use for layout information.
551 /// Components - vcall and vbase offset components
552 typedef SmallVector<VTableComponent, 64> VTableComponentVectorTy;
553 VTableComponentVectorTy Components;
555 /// VisitedVirtualBases - Visited virtual bases.
556 llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedVirtualBases;
558 /// VCallOffsets - Keeps track of vcall offsets.
559 VCallOffsetMap VCallOffsets;
562 /// VBaseOffsetOffsets - Contains the offsets of the virtual base offsets,
563 /// relative to the address point.
564 VBaseOffsetOffsetsMapTy VBaseOffsetOffsets;
566 /// FinalOverriders - The final overriders of the most derived class.
567 /// (Can be null when we're not building a vtable of the most derived class).
568 const FinalOverriders *Overriders;
570 /// AddVCallAndVBaseOffsets - Add vcall offsets and vbase offsets for the
571 /// given base subobject.
572 void AddVCallAndVBaseOffsets(BaseSubobject Base, bool BaseIsVirtual,
573 CharUnits RealBaseOffset);
575 /// AddVCallOffsets - Add vcall offsets for the given base subobject.
576 void AddVCallOffsets(BaseSubobject Base, CharUnits VBaseOffset);
578 /// AddVBaseOffsets - Add vbase offsets for the given class.
579 void AddVBaseOffsets(const CXXRecordDecl *Base,
580 CharUnits OffsetInLayoutClass);
582 /// getCurrentOffsetOffset - Get the current vcall or vbase offset offset in
583 /// chars, relative to the vtable address point.
584 CharUnits getCurrentOffsetOffset() const;
587 VCallAndVBaseOffsetBuilder(const CXXRecordDecl *MostDerivedClass,
588 const CXXRecordDecl *LayoutClass,
589 const FinalOverriders *Overriders,
590 BaseSubobject Base, bool BaseIsVirtual,
591 CharUnits OffsetInLayoutClass)
592 : MostDerivedClass(MostDerivedClass), LayoutClass(LayoutClass),
593 Context(MostDerivedClass->getASTContext()), Overriders(Overriders) {
595 // Add vcall and vbase offsets.
596 AddVCallAndVBaseOffsets(Base, BaseIsVirtual, OffsetInLayoutClass);
599 /// Methods for iterating over the components.
600 typedef VTableComponentVectorTy::const_reverse_iterator const_iterator;
601 const_iterator components_begin() const { return Components.rbegin(); }
602 const_iterator components_end() const { return Components.rend(); }
604 const VCallOffsetMap &getVCallOffsets() const { return VCallOffsets; }
605 const VBaseOffsetOffsetsMapTy &getVBaseOffsetOffsets() const {
606 return VBaseOffsetOffsets;
611 VCallAndVBaseOffsetBuilder::AddVCallAndVBaseOffsets(BaseSubobject Base,
613 CharUnits RealBaseOffset) {
614 const ASTRecordLayout &Layout = Context.getASTRecordLayout(Base.getBase());
616 // Itanium C++ ABI 2.5.2:
617 // ..in classes sharing a virtual table with a primary base class, the vcall
618 // and vbase offsets added by the derived class all come before the vcall
619 // and vbase offsets required by the base class, so that the latter may be
620 // laid out as required by the base class without regard to additions from
621 // the derived class(es).
623 // (Since we're emitting the vcall and vbase offsets in reverse order, we'll
624 // emit them for the primary base first).
625 if (const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase()) {
626 bool PrimaryBaseIsVirtual = Layout.isPrimaryBaseVirtual();
628 CharUnits PrimaryBaseOffset;
630 // Get the base offset of the primary base.
631 if (PrimaryBaseIsVirtual) {
632 assert(Layout.getVBaseClassOffset(PrimaryBase).isZero() &&
633 "Primary vbase should have a zero offset!");
635 const ASTRecordLayout &MostDerivedClassLayout =
636 Context.getASTRecordLayout(MostDerivedClass);
639 MostDerivedClassLayout.getVBaseClassOffset(PrimaryBase);
641 assert(Layout.getBaseClassOffset(PrimaryBase).isZero() &&
642 "Primary base should have a zero offset!");
644 PrimaryBaseOffset = Base.getBaseOffset();
647 AddVCallAndVBaseOffsets(
648 BaseSubobject(PrimaryBase,PrimaryBaseOffset),
649 PrimaryBaseIsVirtual, RealBaseOffset);
652 AddVBaseOffsets(Base.getBase(), RealBaseOffset);
654 // We only want to add vcall offsets for virtual bases.
656 AddVCallOffsets(Base, RealBaseOffset);
659 CharUnits VCallAndVBaseOffsetBuilder::getCurrentOffsetOffset() const {
660 // OffsetIndex is the index of this vcall or vbase offset, relative to the
661 // vtable address point. (We subtract 3 to account for the information just
662 // above the address point, the RTTI info, the offset to top, and the
663 // vcall offset itself).
664 int64_t OffsetIndex = -(int64_t)(3 + Components.size());
666 CharUnits PointerWidth =
667 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
668 CharUnits OffsetOffset = PointerWidth * OffsetIndex;
672 void VCallAndVBaseOffsetBuilder::AddVCallOffsets(BaseSubobject Base,
673 CharUnits VBaseOffset) {
674 const CXXRecordDecl *RD = Base.getBase();
675 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
677 const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
679 // Handle the primary base first.
680 // We only want to add vcall offsets if the base is non-virtual; a virtual
681 // primary base will have its vcall and vbase offsets emitted already.
682 if (PrimaryBase && !Layout.isPrimaryBaseVirtual()) {
683 // Get the base offset of the primary base.
684 assert(Layout.getBaseClassOffset(PrimaryBase).isZero() &&
685 "Primary base should have a zero offset!");
687 AddVCallOffsets(BaseSubobject(PrimaryBase, Base.getBaseOffset()),
691 // Add the vcall offsets.
692 for (const auto *MD : RD->methods()) {
693 if (!MD->isVirtual())
695 MD = MD->getCanonicalDecl();
697 CharUnits OffsetOffset = getCurrentOffsetOffset();
699 // Don't add a vcall offset if we already have one for this member function
701 if (!VCallOffsets.AddVCallOffset(MD, OffsetOffset))
704 CharUnits Offset = CharUnits::Zero();
707 // Get the final overrider.
708 FinalOverriders::OverriderInfo Overrider =
709 Overriders->getOverrider(MD, Base.getBaseOffset());
711 /// The vcall offset is the offset from the virtual base to the object
712 /// where the function was overridden.
713 Offset = Overrider.Offset - VBaseOffset;
716 Components.push_back(
717 VTableComponent::MakeVCallOffset(Offset));
720 // And iterate over all non-virtual bases (ignoring the primary base).
721 for (const auto &B : RD->bases()) {
725 const CXXRecordDecl *BaseDecl = B.getType()->getAsCXXRecordDecl();
726 if (BaseDecl == PrimaryBase)
729 // Get the base offset of this base.
730 CharUnits BaseOffset = Base.getBaseOffset() +
731 Layout.getBaseClassOffset(BaseDecl);
733 AddVCallOffsets(BaseSubobject(BaseDecl, BaseOffset),
739 VCallAndVBaseOffsetBuilder::AddVBaseOffsets(const CXXRecordDecl *RD,
740 CharUnits OffsetInLayoutClass) {
741 const ASTRecordLayout &LayoutClassLayout =
742 Context.getASTRecordLayout(LayoutClass);
744 // Add vbase offsets.
745 for (const auto &B : RD->bases()) {
746 const CXXRecordDecl *BaseDecl = B.getType()->getAsCXXRecordDecl();
748 // Check if this is a virtual base that we haven't visited before.
749 if (B.isVirtual() && VisitedVirtualBases.insert(BaseDecl).second) {
751 LayoutClassLayout.getVBaseClassOffset(BaseDecl) - OffsetInLayoutClass;
753 // Add the vbase offset offset.
754 assert(!VBaseOffsetOffsets.count(BaseDecl) &&
755 "vbase offset offset already exists!");
757 CharUnits VBaseOffsetOffset = getCurrentOffsetOffset();
758 VBaseOffsetOffsets.insert(
759 std::make_pair(BaseDecl, VBaseOffsetOffset));
761 Components.push_back(
762 VTableComponent::MakeVBaseOffset(Offset));
765 // Check the base class looking for more vbase offsets.
766 AddVBaseOffsets(BaseDecl, OffsetInLayoutClass);
770 /// ItaniumVTableBuilder - Class for building vtable layout information.
771 class ItaniumVTableBuilder {
773 /// PrimaryBasesSetVectorTy - A set vector of direct and indirect
775 typedef llvm::SmallSetVector<const CXXRecordDecl *, 8>
776 PrimaryBasesSetVectorTy;
778 typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits>
779 VBaseOffsetOffsetsMapTy;
781 typedef VTableLayout::AddressPointsMapTy AddressPointsMapTy;
783 typedef llvm::DenseMap<GlobalDecl, int64_t> MethodVTableIndicesTy;
786 /// VTables - Global vtable information.
787 ItaniumVTableContext &VTables;
789 /// MostDerivedClass - The most derived class for which we're building this
791 const CXXRecordDecl *MostDerivedClass;
793 /// MostDerivedClassOffset - If we're building a construction vtable, this
794 /// holds the offset from the layout class to the most derived class.
795 const CharUnits MostDerivedClassOffset;
797 /// MostDerivedClassIsVirtual - Whether the most derived class is a virtual
798 /// base. (This only makes sense when building a construction vtable).
799 bool MostDerivedClassIsVirtual;
801 /// LayoutClass - The class we're using for layout information. Will be
802 /// different than the most derived class if we're building a construction
804 const CXXRecordDecl *LayoutClass;
806 /// Context - The ASTContext which we will use for layout information.
809 /// FinalOverriders - The final overriders of the most derived class.
810 const FinalOverriders Overriders;
812 /// VCallOffsetsForVBases - Keeps track of vcall offsets for the virtual
813 /// bases in this vtable.
814 llvm::DenseMap<const CXXRecordDecl *, VCallOffsetMap> VCallOffsetsForVBases;
816 /// VBaseOffsetOffsets - Contains the offsets of the virtual base offsets for
817 /// the most derived class.
818 VBaseOffsetOffsetsMapTy VBaseOffsetOffsets;
820 /// Components - The components of the vtable being built.
821 SmallVector<VTableComponent, 64> Components;
823 /// AddressPoints - Address points for the vtable being built.
824 AddressPointsMapTy AddressPoints;
826 /// MethodInfo - Contains information about a method in a vtable.
827 /// (Used for computing 'this' pointer adjustment thunks.
829 /// BaseOffset - The base offset of this method.
830 const CharUnits BaseOffset;
832 /// BaseOffsetInLayoutClass - The base offset in the layout class of this
834 const CharUnits BaseOffsetInLayoutClass;
836 /// VTableIndex - The index in the vtable that this method has.
837 /// (For destructors, this is the index of the complete destructor).
838 const uint64_t VTableIndex;
840 MethodInfo(CharUnits BaseOffset, CharUnits BaseOffsetInLayoutClass,
841 uint64_t VTableIndex)
842 : BaseOffset(BaseOffset),
843 BaseOffsetInLayoutClass(BaseOffsetInLayoutClass),
844 VTableIndex(VTableIndex) { }
847 : BaseOffset(CharUnits::Zero()),
848 BaseOffsetInLayoutClass(CharUnits::Zero()),
852 typedef llvm::DenseMap<const CXXMethodDecl *, MethodInfo> MethodInfoMapTy;
854 /// MethodInfoMap - The information for all methods in the vtable we're
855 /// currently building.
856 MethodInfoMapTy MethodInfoMap;
858 /// MethodVTableIndices - Contains the index (relative to the vtable address
859 /// point) where the function pointer for a virtual function is stored.
860 MethodVTableIndicesTy MethodVTableIndices;
862 typedef llvm::DenseMap<uint64_t, ThunkInfo> VTableThunksMapTy;
864 /// VTableThunks - The thunks by vtable index in the vtable currently being
866 VTableThunksMapTy VTableThunks;
868 typedef SmallVector<ThunkInfo, 1> ThunkInfoVectorTy;
869 typedef llvm::DenseMap<const CXXMethodDecl *, ThunkInfoVectorTy> ThunksMapTy;
871 /// Thunks - A map that contains all the thunks needed for all methods in the
872 /// most derived class for which the vtable is currently being built.
875 /// AddThunk - Add a thunk for the given method.
876 void AddThunk(const CXXMethodDecl *MD, const ThunkInfo &Thunk);
878 /// ComputeThisAdjustments - Compute the 'this' pointer adjustments for the
879 /// part of the vtable we're currently building.
880 void ComputeThisAdjustments();
882 typedef llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedVirtualBasesSetTy;
884 /// PrimaryVirtualBases - All known virtual bases who are a primary base of
886 VisitedVirtualBasesSetTy PrimaryVirtualBases;
888 /// ComputeReturnAdjustment - Compute the return adjustment given a return
889 /// adjustment base offset.
890 ReturnAdjustment ComputeReturnAdjustment(BaseOffset Offset);
892 /// ComputeThisAdjustmentBaseOffset - Compute the base offset for adjusting
893 /// the 'this' pointer from the base subobject to the derived subobject.
894 BaseOffset ComputeThisAdjustmentBaseOffset(BaseSubobject Base,
895 BaseSubobject Derived) const;
897 /// ComputeThisAdjustment - Compute the 'this' pointer adjustment for the
898 /// given virtual member function, its offset in the layout class and its
901 ComputeThisAdjustment(const CXXMethodDecl *MD,
902 CharUnits BaseOffsetInLayoutClass,
903 FinalOverriders::OverriderInfo Overrider);
905 /// AddMethod - Add a single virtual member function to the vtable
906 /// components vector.
907 void AddMethod(const CXXMethodDecl *MD, ReturnAdjustment ReturnAdjustment);
909 /// IsOverriderUsed - Returns whether the overrider will ever be used in this
910 /// part of the vtable.
912 /// Itanium C++ ABI 2.5.2:
914 /// struct A { virtual void f(); };
915 /// struct B : virtual public A { int i; };
916 /// struct C : virtual public A { int j; };
917 /// struct D : public B, public C {};
919 /// When B and C are declared, A is a primary base in each case, so although
920 /// vcall offsets are allocated in the A-in-B and A-in-C vtables, no this
921 /// adjustment is required and no thunk is generated. However, inside D
922 /// objects, A is no longer a primary base of C, so if we allowed calls to
923 /// C::f() to use the copy of A's vtable in the C subobject, we would need
924 /// to adjust this from C* to B::A*, which would require a third-party
925 /// thunk. Since we require that a call to C::f() first convert to A*,
926 /// C-in-D's copy of A's vtable is never referenced, so this is not
928 bool IsOverriderUsed(const CXXMethodDecl *Overrider,
929 CharUnits BaseOffsetInLayoutClass,
930 const CXXRecordDecl *FirstBaseInPrimaryBaseChain,
931 CharUnits FirstBaseOffsetInLayoutClass) const;
934 /// AddMethods - Add the methods of this base subobject and all its
935 /// primary bases to the vtable components vector.
936 void AddMethods(BaseSubobject Base, CharUnits BaseOffsetInLayoutClass,
937 const CXXRecordDecl *FirstBaseInPrimaryBaseChain,
938 CharUnits FirstBaseOffsetInLayoutClass,
939 PrimaryBasesSetVectorTy &PrimaryBases);
941 // LayoutVTable - Layout the vtable for the given base class, including its
942 // secondary vtables and any vtables for virtual bases.
945 /// LayoutPrimaryAndSecondaryVTables - Layout the primary vtable for the
946 /// given base subobject, as well as all its secondary vtables.
948 /// \param BaseIsMorallyVirtual whether the base subobject is a virtual base
949 /// or a direct or indirect base of a virtual base.
951 /// \param BaseIsVirtualInLayoutClass - Whether the base subobject is virtual
952 /// in the layout class.
953 void LayoutPrimaryAndSecondaryVTables(BaseSubobject Base,
954 bool BaseIsMorallyVirtual,
955 bool BaseIsVirtualInLayoutClass,
956 CharUnits OffsetInLayoutClass);
958 /// LayoutSecondaryVTables - Layout the secondary vtables for the given base
961 /// \param BaseIsMorallyVirtual whether the base subobject is a virtual base
962 /// or a direct or indirect base of a virtual base.
963 void LayoutSecondaryVTables(BaseSubobject Base, bool BaseIsMorallyVirtual,
964 CharUnits OffsetInLayoutClass);
966 /// DeterminePrimaryVirtualBases - Determine the primary virtual bases in this
968 void DeterminePrimaryVirtualBases(const CXXRecordDecl *RD,
969 CharUnits OffsetInLayoutClass,
970 VisitedVirtualBasesSetTy &VBases);
972 /// LayoutVTablesForVirtualBases - Layout vtables for all virtual bases of the
973 /// given base (excluding any primary bases).
974 void LayoutVTablesForVirtualBases(const CXXRecordDecl *RD,
975 VisitedVirtualBasesSetTy &VBases);
977 /// isBuildingConstructionVTable - Return whether this vtable builder is
978 /// building a construction vtable.
979 bool isBuildingConstructorVTable() const {
980 return MostDerivedClass != LayoutClass;
984 /// Component indices of the first component of each of the vtables in the
986 SmallVector<size_t, 4> VTableIndices;
988 ItaniumVTableBuilder(ItaniumVTableContext &VTables,
989 const CXXRecordDecl *MostDerivedClass,
990 CharUnits MostDerivedClassOffset,
991 bool MostDerivedClassIsVirtual,
992 const CXXRecordDecl *LayoutClass)
993 : VTables(VTables), MostDerivedClass(MostDerivedClass),
994 MostDerivedClassOffset(MostDerivedClassOffset),
995 MostDerivedClassIsVirtual(MostDerivedClassIsVirtual),
996 LayoutClass(LayoutClass), Context(MostDerivedClass->getASTContext()),
997 Overriders(MostDerivedClass, MostDerivedClassOffset, LayoutClass) {
998 assert(!Context.getTargetInfo().getCXXABI().isMicrosoft());
1002 if (Context.getLangOpts().DumpVTableLayouts)
1003 dumpLayout(llvm::outs());
1006 uint64_t getNumThunks() const {
1007 return Thunks.size();
1010 ThunksMapTy::const_iterator thunks_begin() const {
1011 return Thunks.begin();
1014 ThunksMapTy::const_iterator thunks_end() const {
1015 return Thunks.end();
1018 const VBaseOffsetOffsetsMapTy &getVBaseOffsetOffsets() const {
1019 return VBaseOffsetOffsets;
1022 const AddressPointsMapTy &getAddressPoints() const {
1023 return AddressPoints;
1026 MethodVTableIndicesTy::const_iterator vtable_indices_begin() const {
1027 return MethodVTableIndices.begin();
1030 MethodVTableIndicesTy::const_iterator vtable_indices_end() const {
1031 return MethodVTableIndices.end();
1034 ArrayRef<VTableComponent> vtable_components() const { return Components; }
1036 AddressPointsMapTy::const_iterator address_points_begin() const {
1037 return AddressPoints.begin();
1040 AddressPointsMapTy::const_iterator address_points_end() const {
1041 return AddressPoints.end();
1044 VTableThunksMapTy::const_iterator vtable_thunks_begin() const {
1045 return VTableThunks.begin();
1048 VTableThunksMapTy::const_iterator vtable_thunks_end() const {
1049 return VTableThunks.end();
1052 /// dumpLayout - Dump the vtable layout.
1053 void dumpLayout(raw_ostream&);
1056 void ItaniumVTableBuilder::AddThunk(const CXXMethodDecl *MD,
1057 const ThunkInfo &Thunk) {
1058 assert(!isBuildingConstructorVTable() &&
1059 "Can't add thunks for construction vtable");
1061 SmallVectorImpl<ThunkInfo> &ThunksVector = Thunks[MD];
1063 // Check if we have this thunk already.
1064 if (std::find(ThunksVector.begin(), ThunksVector.end(), Thunk) !=
1068 ThunksVector.push_back(Thunk);
1071 typedef llvm::SmallPtrSet<const CXXMethodDecl *, 8> OverriddenMethodsSetTy;
1073 /// Visit all the methods overridden by the given method recursively,
1074 /// in a depth-first pre-order. The Visitor's visitor method returns a bool
1075 /// indicating whether to continue the recursion for the given overridden
1076 /// method (i.e. returning false stops the iteration).
1077 template <class VisitorTy>
1079 visitAllOverriddenMethods(const CXXMethodDecl *MD, VisitorTy &Visitor) {
1080 assert(MD->isVirtual() && "Method is not virtual!");
1082 for (CXXMethodDecl::method_iterator I = MD->begin_overridden_methods(),
1083 E = MD->end_overridden_methods(); I != E; ++I) {
1084 const CXXMethodDecl *OverriddenMD = *I;
1085 if (!Visitor(OverriddenMD))
1087 visitAllOverriddenMethods(OverriddenMD, Visitor);
1091 /// ComputeAllOverriddenMethods - Given a method decl, will return a set of all
1092 /// the overridden methods that the function decl overrides.
1094 ComputeAllOverriddenMethods(const CXXMethodDecl *MD,
1095 OverriddenMethodsSetTy& OverriddenMethods) {
1096 auto OverriddenMethodsCollector = [&](const CXXMethodDecl *MD) {
1097 // Don't recurse on this method if we've already collected it.
1098 return OverriddenMethods.insert(MD).second;
1100 visitAllOverriddenMethods(MD, OverriddenMethodsCollector);
1103 void ItaniumVTableBuilder::ComputeThisAdjustments() {
1104 // Now go through the method info map and see if any of the methods need
1105 // 'this' pointer adjustments.
1106 for (const auto &MI : MethodInfoMap) {
1107 const CXXMethodDecl *MD = MI.first;
1108 const MethodInfo &MethodInfo = MI.second;
1110 // Ignore adjustments for unused function pointers.
1111 uint64_t VTableIndex = MethodInfo.VTableIndex;
1112 if (Components[VTableIndex].getKind() ==
1113 VTableComponent::CK_UnusedFunctionPointer)
1116 // Get the final overrider for this method.
1117 FinalOverriders::OverriderInfo Overrider =
1118 Overriders.getOverrider(MD, MethodInfo.BaseOffset);
1120 // Check if we need an adjustment at all.
1121 if (MethodInfo.BaseOffsetInLayoutClass == Overrider.Offset) {
1122 // When a return thunk is needed by a derived class that overrides a
1123 // virtual base, gcc uses a virtual 'this' adjustment as well.
1124 // While the thunk itself might be needed by vtables in subclasses or
1125 // in construction vtables, there doesn't seem to be a reason for using
1126 // the thunk in this vtable. Still, we do so to match gcc.
1127 if (VTableThunks.lookup(VTableIndex).Return.isEmpty())
1131 ThisAdjustment ThisAdjustment =
1132 ComputeThisAdjustment(MD, MethodInfo.BaseOffsetInLayoutClass, Overrider);
1134 if (ThisAdjustment.isEmpty())
1138 VTableThunks[VTableIndex].This = ThisAdjustment;
1140 if (isa<CXXDestructorDecl>(MD)) {
1141 // Add an adjustment for the deleting destructor as well.
1142 VTableThunks[VTableIndex + 1].This = ThisAdjustment;
1146 /// Clear the method info map.
1147 MethodInfoMap.clear();
1149 if (isBuildingConstructorVTable()) {
1150 // We don't need to store thunk information for construction vtables.
1154 for (const auto &TI : VTableThunks) {
1155 const VTableComponent &Component = Components[TI.first];
1156 const ThunkInfo &Thunk = TI.second;
1157 const CXXMethodDecl *MD;
1159 switch (Component.getKind()) {
1161 llvm_unreachable("Unexpected vtable component kind!");
1162 case VTableComponent::CK_FunctionPointer:
1163 MD = Component.getFunctionDecl();
1165 case VTableComponent::CK_CompleteDtorPointer:
1166 MD = Component.getDestructorDecl();
1168 case VTableComponent::CK_DeletingDtorPointer:
1169 // We've already added the thunk when we saw the complete dtor pointer.
1173 if (MD->getParent() == MostDerivedClass)
1174 AddThunk(MD, Thunk);
1179 ItaniumVTableBuilder::ComputeReturnAdjustment(BaseOffset Offset) {
1180 ReturnAdjustment Adjustment;
1182 if (!Offset.isEmpty()) {
1183 if (Offset.VirtualBase) {
1184 // Get the virtual base offset offset.
1185 if (Offset.DerivedClass == MostDerivedClass) {
1186 // We can get the offset offset directly from our map.
1187 Adjustment.Virtual.Itanium.VBaseOffsetOffset =
1188 VBaseOffsetOffsets.lookup(Offset.VirtualBase).getQuantity();
1190 Adjustment.Virtual.Itanium.VBaseOffsetOffset =
1191 VTables.getVirtualBaseOffsetOffset(Offset.DerivedClass,
1192 Offset.VirtualBase).getQuantity();
1196 Adjustment.NonVirtual = Offset.NonVirtualOffset.getQuantity();
1202 BaseOffset ItaniumVTableBuilder::ComputeThisAdjustmentBaseOffset(
1203 BaseSubobject Base, BaseSubobject Derived) const {
1204 const CXXRecordDecl *BaseRD = Base.getBase();
1205 const CXXRecordDecl *DerivedRD = Derived.getBase();
1207 CXXBasePaths Paths(/*FindAmbiguities=*/true,
1208 /*RecordPaths=*/true, /*DetectVirtual=*/true);
1210 if (!DerivedRD->isDerivedFrom(BaseRD, Paths))
1211 llvm_unreachable("Class must be derived from the passed in base class!");
1213 // We have to go through all the paths, and see which one leads us to the
1214 // right base subobject.
1215 for (const CXXBasePath &Path : Paths) {
1216 BaseOffset Offset = ComputeBaseOffset(Context, DerivedRD, Path);
1218 CharUnits OffsetToBaseSubobject = Offset.NonVirtualOffset;
1220 if (Offset.VirtualBase) {
1221 // If we have a virtual base class, the non-virtual offset is relative
1222 // to the virtual base class offset.
1223 const ASTRecordLayout &LayoutClassLayout =
1224 Context.getASTRecordLayout(LayoutClass);
1226 /// Get the virtual base offset, relative to the most derived class
1228 OffsetToBaseSubobject +=
1229 LayoutClassLayout.getVBaseClassOffset(Offset.VirtualBase);
1231 // Otherwise, the non-virtual offset is relative to the derived class
1233 OffsetToBaseSubobject += Derived.getBaseOffset();
1236 // Check if this path gives us the right base subobject.
1237 if (OffsetToBaseSubobject == Base.getBaseOffset()) {
1238 // Since we're going from the base class _to_ the derived class, we'll
1239 // invert the non-virtual offset here.
1240 Offset.NonVirtualOffset = -Offset.NonVirtualOffset;
1245 return BaseOffset();
1248 ThisAdjustment ItaniumVTableBuilder::ComputeThisAdjustment(
1249 const CXXMethodDecl *MD, CharUnits BaseOffsetInLayoutClass,
1250 FinalOverriders::OverriderInfo Overrider) {
1251 // Ignore adjustments for pure virtual member functions.
1252 if (Overrider.Method->isPure())
1253 return ThisAdjustment();
1255 BaseSubobject OverriddenBaseSubobject(MD->getParent(),
1256 BaseOffsetInLayoutClass);
1258 BaseSubobject OverriderBaseSubobject(Overrider.Method->getParent(),
1261 // Compute the adjustment offset.
1262 BaseOffset Offset = ComputeThisAdjustmentBaseOffset(OverriddenBaseSubobject,
1263 OverriderBaseSubobject);
1264 if (Offset.isEmpty())
1265 return ThisAdjustment();
1267 ThisAdjustment Adjustment;
1269 if (Offset.VirtualBase) {
1270 // Get the vcall offset map for this virtual base.
1271 VCallOffsetMap &VCallOffsets = VCallOffsetsForVBases[Offset.VirtualBase];
1273 if (VCallOffsets.empty()) {
1274 // We don't have vcall offsets for this virtual base, go ahead and
1276 VCallAndVBaseOffsetBuilder Builder(MostDerivedClass, MostDerivedClass,
1277 /*FinalOverriders=*/nullptr,
1278 BaseSubobject(Offset.VirtualBase,
1280 /*BaseIsVirtual=*/true,
1281 /*OffsetInLayoutClass=*/
1284 VCallOffsets = Builder.getVCallOffsets();
1287 Adjustment.Virtual.Itanium.VCallOffsetOffset =
1288 VCallOffsets.getVCallOffsetOffset(MD).getQuantity();
1291 // Set the non-virtual part of the adjustment.
1292 Adjustment.NonVirtual = Offset.NonVirtualOffset.getQuantity();
1297 void ItaniumVTableBuilder::AddMethod(const CXXMethodDecl *MD,
1298 ReturnAdjustment ReturnAdjustment) {
1299 if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) {
1300 assert(ReturnAdjustment.isEmpty() &&
1301 "Destructor can't have return adjustment!");
1303 // Add both the complete destructor and the deleting destructor.
1304 Components.push_back(VTableComponent::MakeCompleteDtor(DD));
1305 Components.push_back(VTableComponent::MakeDeletingDtor(DD));
1307 // Add the return adjustment if necessary.
1308 if (!ReturnAdjustment.isEmpty())
1309 VTableThunks[Components.size()].Return = ReturnAdjustment;
1311 // Add the function.
1312 Components.push_back(VTableComponent::MakeFunction(MD));
1316 /// OverridesIndirectMethodInBase - Return whether the given member function
1317 /// overrides any methods in the set of given bases.
1318 /// Unlike OverridesMethodInBase, this checks "overriders of overriders".
1319 /// For example, if we have:
1321 /// struct A { virtual void f(); }
1322 /// struct B : A { virtual void f(); }
1323 /// struct C : B { virtual void f(); }
1325 /// OverridesIndirectMethodInBase will return true if given C::f as the method
1326 /// and { A } as the set of bases.
1327 static bool OverridesIndirectMethodInBases(
1328 const CXXMethodDecl *MD,
1329 ItaniumVTableBuilder::PrimaryBasesSetVectorTy &Bases) {
1330 if (Bases.count(MD->getParent()))
1333 for (CXXMethodDecl::method_iterator I = MD->begin_overridden_methods(),
1334 E = MD->end_overridden_methods(); I != E; ++I) {
1335 const CXXMethodDecl *OverriddenMD = *I;
1337 // Check "indirect overriders".
1338 if (OverridesIndirectMethodInBases(OverriddenMD, Bases))
1345 bool ItaniumVTableBuilder::IsOverriderUsed(
1346 const CXXMethodDecl *Overrider, CharUnits BaseOffsetInLayoutClass,
1347 const CXXRecordDecl *FirstBaseInPrimaryBaseChain,
1348 CharUnits FirstBaseOffsetInLayoutClass) const {
1349 // If the base and the first base in the primary base chain have the same
1350 // offsets, then this overrider will be used.
1351 if (BaseOffsetInLayoutClass == FirstBaseOffsetInLayoutClass)
1354 // We know now that Base (or a direct or indirect base of it) is a primary
1355 // base in part of the class hierarchy, but not a primary base in the most
1358 // If the overrider is the first base in the primary base chain, we know
1359 // that the overrider will be used.
1360 if (Overrider->getParent() == FirstBaseInPrimaryBaseChain)
1363 ItaniumVTableBuilder::PrimaryBasesSetVectorTy PrimaryBases;
1365 const CXXRecordDecl *RD = FirstBaseInPrimaryBaseChain;
1366 PrimaryBases.insert(RD);
1368 // Now traverse the base chain, starting with the first base, until we find
1369 // the base that is no longer a primary base.
1371 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
1372 const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
1377 if (Layout.isPrimaryBaseVirtual()) {
1378 assert(Layout.getVBaseClassOffset(PrimaryBase).isZero() &&
1379 "Primary base should always be at offset 0!");
1381 const ASTRecordLayout &LayoutClassLayout =
1382 Context.getASTRecordLayout(LayoutClass);
1384 // Now check if this is the primary base that is not a primary base in the
1385 // most derived class.
1386 if (LayoutClassLayout.getVBaseClassOffset(PrimaryBase) !=
1387 FirstBaseOffsetInLayoutClass) {
1388 // We found it, stop walking the chain.
1392 assert(Layout.getBaseClassOffset(PrimaryBase).isZero() &&
1393 "Primary base should always be at offset 0!");
1396 if (!PrimaryBases.insert(PrimaryBase))
1397 llvm_unreachable("Found a duplicate primary base!");
1402 // If the final overrider is an override of one of the primary bases,
1403 // then we know that it will be used.
1404 return OverridesIndirectMethodInBases(Overrider, PrimaryBases);
1407 typedef llvm::SmallSetVector<const CXXRecordDecl *, 8> BasesSetVectorTy;
1409 /// FindNearestOverriddenMethod - Given a method, returns the overridden method
1410 /// from the nearest base. Returns null if no method was found.
1411 /// The Bases are expected to be sorted in a base-to-derived order.
1412 static const CXXMethodDecl *
1413 FindNearestOverriddenMethod(const CXXMethodDecl *MD,
1414 BasesSetVectorTy &Bases) {
1415 OverriddenMethodsSetTy OverriddenMethods;
1416 ComputeAllOverriddenMethods(MD, OverriddenMethods);
1418 for (const CXXRecordDecl *PrimaryBase :
1419 llvm::make_range(Bases.rbegin(), Bases.rend())) {
1420 // Now check the overridden methods.
1421 for (const CXXMethodDecl *OverriddenMD : OverriddenMethods) {
1422 // We found our overridden method.
1423 if (OverriddenMD->getParent() == PrimaryBase)
1424 return OverriddenMD;
1431 void ItaniumVTableBuilder::AddMethods(
1432 BaseSubobject Base, CharUnits BaseOffsetInLayoutClass,
1433 const CXXRecordDecl *FirstBaseInPrimaryBaseChain,
1434 CharUnits FirstBaseOffsetInLayoutClass,
1435 PrimaryBasesSetVectorTy &PrimaryBases) {
1436 // Itanium C++ ABI 2.5.2:
1437 // The order of the virtual function pointers in a virtual table is the
1438 // order of declaration of the corresponding member functions in the class.
1440 // There is an entry for any virtual function declared in a class,
1441 // whether it is a new function or overrides a base class function,
1442 // unless it overrides a function from the primary base, and conversion
1443 // between their return types does not require an adjustment.
1445 const CXXRecordDecl *RD = Base.getBase();
1446 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
1448 if (const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase()) {
1449 CharUnits PrimaryBaseOffset;
1450 CharUnits PrimaryBaseOffsetInLayoutClass;
1451 if (Layout.isPrimaryBaseVirtual()) {
1452 assert(Layout.getVBaseClassOffset(PrimaryBase).isZero() &&
1453 "Primary vbase should have a zero offset!");
1455 const ASTRecordLayout &MostDerivedClassLayout =
1456 Context.getASTRecordLayout(MostDerivedClass);
1459 MostDerivedClassLayout.getVBaseClassOffset(PrimaryBase);
1461 const ASTRecordLayout &LayoutClassLayout =
1462 Context.getASTRecordLayout(LayoutClass);
1464 PrimaryBaseOffsetInLayoutClass =
1465 LayoutClassLayout.getVBaseClassOffset(PrimaryBase);
1467 assert(Layout.getBaseClassOffset(PrimaryBase).isZero() &&
1468 "Primary base should have a zero offset!");
1470 PrimaryBaseOffset = Base.getBaseOffset();
1471 PrimaryBaseOffsetInLayoutClass = BaseOffsetInLayoutClass;
1474 AddMethods(BaseSubobject(PrimaryBase, PrimaryBaseOffset),
1475 PrimaryBaseOffsetInLayoutClass, FirstBaseInPrimaryBaseChain,
1476 FirstBaseOffsetInLayoutClass, PrimaryBases);
1478 if (!PrimaryBases.insert(PrimaryBase))
1479 llvm_unreachable("Found a duplicate primary base!");
1482 const CXXDestructorDecl *ImplicitVirtualDtor = nullptr;
1484 typedef llvm::SmallVector<const CXXMethodDecl *, 8> NewVirtualFunctionsTy;
1485 NewVirtualFunctionsTy NewVirtualFunctions;
1487 // Now go through all virtual member functions and add them.
1488 for (const auto *MD : RD->methods()) {
1489 if (!MD->isVirtual())
1491 MD = MD->getCanonicalDecl();
1493 // Get the final overrider.
1494 FinalOverriders::OverriderInfo Overrider =
1495 Overriders.getOverrider(MD, Base.getBaseOffset());
1497 // Check if this virtual member function overrides a method in a primary
1498 // base. If this is the case, and the return type doesn't require adjustment
1499 // then we can just use the member function from the primary base.
1500 if (const CXXMethodDecl *OverriddenMD =
1501 FindNearestOverriddenMethod(MD, PrimaryBases)) {
1502 if (ComputeReturnAdjustmentBaseOffset(Context, MD,
1503 OverriddenMD).isEmpty()) {
1504 // Replace the method info of the overridden method with our own
1506 assert(MethodInfoMap.count(OverriddenMD) &&
1507 "Did not find the overridden method!");
1508 MethodInfo &OverriddenMethodInfo = MethodInfoMap[OverriddenMD];
1510 MethodInfo MethodInfo(Base.getBaseOffset(), BaseOffsetInLayoutClass,
1511 OverriddenMethodInfo.VTableIndex);
1513 assert(!MethodInfoMap.count(MD) &&
1514 "Should not have method info for this method yet!");
1516 MethodInfoMap.insert(std::make_pair(MD, MethodInfo));
1517 MethodInfoMap.erase(OverriddenMD);
1519 // If the overridden method exists in a virtual base class or a direct
1520 // or indirect base class of a virtual base class, we need to emit a
1521 // thunk if we ever have a class hierarchy where the base class is not
1522 // a primary base in the complete object.
1523 if (!isBuildingConstructorVTable() && OverriddenMD != MD) {
1524 // Compute the this adjustment.
1525 ThisAdjustment ThisAdjustment =
1526 ComputeThisAdjustment(OverriddenMD, BaseOffsetInLayoutClass,
1529 if (ThisAdjustment.Virtual.Itanium.VCallOffsetOffset &&
1530 Overrider.Method->getParent() == MostDerivedClass) {
1532 // There's no return adjustment from OverriddenMD and MD,
1533 // but that doesn't mean there isn't one between MD and
1534 // the final overrider.
1535 BaseOffset ReturnAdjustmentOffset =
1536 ComputeReturnAdjustmentBaseOffset(Context, Overrider.Method, MD);
1537 ReturnAdjustment ReturnAdjustment =
1538 ComputeReturnAdjustment(ReturnAdjustmentOffset);
1540 // This is a virtual thunk for the most derived class, add it.
1541 AddThunk(Overrider.Method,
1542 ThunkInfo(ThisAdjustment, ReturnAdjustment));
1550 if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) {
1551 if (MD->isImplicit()) {
1552 // Itanium C++ ABI 2.5.2:
1553 // If a class has an implicitly-defined virtual destructor,
1554 // its entries come after the declared virtual function pointers.
1556 assert(!ImplicitVirtualDtor &&
1557 "Did already see an implicit virtual dtor!");
1558 ImplicitVirtualDtor = DD;
1563 NewVirtualFunctions.push_back(MD);
1566 if (ImplicitVirtualDtor)
1567 NewVirtualFunctions.push_back(ImplicitVirtualDtor);
1569 for (const CXXMethodDecl *MD : NewVirtualFunctions) {
1570 // Get the final overrider.
1571 FinalOverriders::OverriderInfo Overrider =
1572 Overriders.getOverrider(MD, Base.getBaseOffset());
1574 // Insert the method info for this method.
1575 MethodInfo MethodInfo(Base.getBaseOffset(), BaseOffsetInLayoutClass,
1578 assert(!MethodInfoMap.count(MD) &&
1579 "Should not have method info for this method yet!");
1580 MethodInfoMap.insert(std::make_pair(MD, MethodInfo));
1582 // Check if this overrider is going to be used.
1583 const CXXMethodDecl *OverriderMD = Overrider.Method;
1584 if (!IsOverriderUsed(OverriderMD, BaseOffsetInLayoutClass,
1585 FirstBaseInPrimaryBaseChain,
1586 FirstBaseOffsetInLayoutClass)) {
1587 Components.push_back(VTableComponent::MakeUnusedFunction(OverriderMD));
1591 // Check if this overrider needs a return adjustment.
1592 // We don't want to do this for pure virtual member functions.
1593 BaseOffset ReturnAdjustmentOffset;
1594 if (!OverriderMD->isPure()) {
1595 ReturnAdjustmentOffset =
1596 ComputeReturnAdjustmentBaseOffset(Context, OverriderMD, MD);
1599 ReturnAdjustment ReturnAdjustment =
1600 ComputeReturnAdjustment(ReturnAdjustmentOffset);
1602 AddMethod(Overrider.Method, ReturnAdjustment);
1606 void ItaniumVTableBuilder::LayoutVTable() {
1607 LayoutPrimaryAndSecondaryVTables(BaseSubobject(MostDerivedClass,
1609 /*BaseIsMorallyVirtual=*/false,
1610 MostDerivedClassIsVirtual,
1611 MostDerivedClassOffset);
1613 VisitedVirtualBasesSetTy VBases;
1615 // Determine the primary virtual bases.
1616 DeterminePrimaryVirtualBases(MostDerivedClass, MostDerivedClassOffset,
1620 LayoutVTablesForVirtualBases(MostDerivedClass, VBases);
1622 // -fapple-kext adds an extra entry at end of vtbl.
1623 bool IsAppleKext = Context.getLangOpts().AppleKext;
1625 Components.push_back(VTableComponent::MakeVCallOffset(CharUnits::Zero()));
1628 void ItaniumVTableBuilder::LayoutPrimaryAndSecondaryVTables(
1629 BaseSubobject Base, bool BaseIsMorallyVirtual,
1630 bool BaseIsVirtualInLayoutClass, CharUnits OffsetInLayoutClass) {
1631 assert(Base.getBase()->isDynamicClass() && "class does not have a vtable!");
1633 unsigned VTableIndex = Components.size();
1634 VTableIndices.push_back(VTableIndex);
1636 // Add vcall and vbase offsets for this vtable.
1637 VCallAndVBaseOffsetBuilder Builder(MostDerivedClass, LayoutClass, &Overriders,
1638 Base, BaseIsVirtualInLayoutClass,
1639 OffsetInLayoutClass);
1640 Components.append(Builder.components_begin(), Builder.components_end());
1642 // Check if we need to add these vcall offsets.
1643 if (BaseIsVirtualInLayoutClass && !Builder.getVCallOffsets().empty()) {
1644 VCallOffsetMap &VCallOffsets = VCallOffsetsForVBases[Base.getBase()];
1646 if (VCallOffsets.empty())
1647 VCallOffsets = Builder.getVCallOffsets();
1650 // If we're laying out the most derived class we want to keep track of the
1651 // virtual base class offset offsets.
1652 if (Base.getBase() == MostDerivedClass)
1653 VBaseOffsetOffsets = Builder.getVBaseOffsetOffsets();
1655 // Add the offset to top.
1656 CharUnits OffsetToTop = MostDerivedClassOffset - OffsetInLayoutClass;
1657 Components.push_back(VTableComponent::MakeOffsetToTop(OffsetToTop));
1659 // Next, add the RTTI.
1660 Components.push_back(VTableComponent::MakeRTTI(MostDerivedClass));
1662 uint64_t AddressPoint = Components.size();
1664 // Now go through all virtual member functions and add them.
1665 PrimaryBasesSetVectorTy PrimaryBases;
1666 AddMethods(Base, OffsetInLayoutClass,
1667 Base.getBase(), OffsetInLayoutClass,
1670 const CXXRecordDecl *RD = Base.getBase();
1671 if (RD == MostDerivedClass) {
1672 assert(MethodVTableIndices.empty());
1673 for (const auto &I : MethodInfoMap) {
1674 const CXXMethodDecl *MD = I.first;
1675 const MethodInfo &MI = I.second;
1676 if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) {
1677 MethodVTableIndices[GlobalDecl(DD, Dtor_Complete)]
1678 = MI.VTableIndex - AddressPoint;
1679 MethodVTableIndices[GlobalDecl(DD, Dtor_Deleting)]
1680 = MI.VTableIndex + 1 - AddressPoint;
1682 MethodVTableIndices[MD] = MI.VTableIndex - AddressPoint;
1687 // Compute 'this' pointer adjustments.
1688 ComputeThisAdjustments();
1690 // Add all address points.
1692 AddressPoints.insert(
1693 std::make_pair(BaseSubobject(RD, OffsetInLayoutClass),
1694 VTableLayout::AddressPointLocation{
1695 unsigned(VTableIndices.size() - 1),
1696 unsigned(AddressPoint - VTableIndex)}));
1698 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
1699 const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
1704 if (Layout.isPrimaryBaseVirtual()) {
1705 // Check if this virtual primary base is a primary base in the layout
1706 // class. If it's not, we don't want to add it.
1707 const ASTRecordLayout &LayoutClassLayout =
1708 Context.getASTRecordLayout(LayoutClass);
1710 if (LayoutClassLayout.getVBaseClassOffset(PrimaryBase) !=
1711 OffsetInLayoutClass) {
1712 // We don't want to add this class (or any of its primary bases).
1720 // Layout secondary vtables.
1721 LayoutSecondaryVTables(Base, BaseIsMorallyVirtual, OffsetInLayoutClass);
1725 ItaniumVTableBuilder::LayoutSecondaryVTables(BaseSubobject Base,
1726 bool BaseIsMorallyVirtual,
1727 CharUnits OffsetInLayoutClass) {
1728 // Itanium C++ ABI 2.5.2:
1729 // Following the primary virtual table of a derived class are secondary
1730 // virtual tables for each of its proper base classes, except any primary
1731 // base(s) with which it shares its primary virtual table.
1733 const CXXRecordDecl *RD = Base.getBase();
1734 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
1735 const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
1737 for (const auto &B : RD->bases()) {
1738 // Ignore virtual bases, we'll emit them later.
1742 const CXXRecordDecl *BaseDecl = B.getType()->getAsCXXRecordDecl();
1744 // Ignore bases that don't have a vtable.
1745 if (!BaseDecl->isDynamicClass())
1748 if (isBuildingConstructorVTable()) {
1749 // Itanium C++ ABI 2.6.4:
1750 // Some of the base class subobjects may not need construction virtual
1751 // tables, which will therefore not be present in the construction
1752 // virtual table group, even though the subobject virtual tables are
1753 // present in the main virtual table group for the complete object.
1754 if (!BaseIsMorallyVirtual && !BaseDecl->getNumVBases())
1758 // Get the base offset of this base.
1759 CharUnits RelativeBaseOffset = Layout.getBaseClassOffset(BaseDecl);
1760 CharUnits BaseOffset = Base.getBaseOffset() + RelativeBaseOffset;
1762 CharUnits BaseOffsetInLayoutClass =
1763 OffsetInLayoutClass + RelativeBaseOffset;
1765 // Don't emit a secondary vtable for a primary base. We might however want
1766 // to emit secondary vtables for other bases of this base.
1767 if (BaseDecl == PrimaryBase) {
1768 LayoutSecondaryVTables(BaseSubobject(BaseDecl, BaseOffset),
1769 BaseIsMorallyVirtual, BaseOffsetInLayoutClass);
1773 // Layout the primary vtable (and any secondary vtables) for this base.
1774 LayoutPrimaryAndSecondaryVTables(
1775 BaseSubobject(BaseDecl, BaseOffset),
1776 BaseIsMorallyVirtual,
1777 /*BaseIsVirtualInLayoutClass=*/false,
1778 BaseOffsetInLayoutClass);
1782 void ItaniumVTableBuilder::DeterminePrimaryVirtualBases(
1783 const CXXRecordDecl *RD, CharUnits OffsetInLayoutClass,
1784 VisitedVirtualBasesSetTy &VBases) {
1785 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
1787 // Check if this base has a primary base.
1788 if (const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase()) {
1790 // Check if it's virtual.
1791 if (Layout.isPrimaryBaseVirtual()) {
1792 bool IsPrimaryVirtualBase = true;
1794 if (isBuildingConstructorVTable()) {
1795 // Check if the base is actually a primary base in the class we use for
1797 const ASTRecordLayout &LayoutClassLayout =
1798 Context.getASTRecordLayout(LayoutClass);
1800 CharUnits PrimaryBaseOffsetInLayoutClass =
1801 LayoutClassLayout.getVBaseClassOffset(PrimaryBase);
1803 // We know that the base is not a primary base in the layout class if
1804 // the base offsets are different.
1805 if (PrimaryBaseOffsetInLayoutClass != OffsetInLayoutClass)
1806 IsPrimaryVirtualBase = false;
1809 if (IsPrimaryVirtualBase)
1810 PrimaryVirtualBases.insert(PrimaryBase);
1814 // Traverse bases, looking for more primary virtual bases.
1815 for (const auto &B : RD->bases()) {
1816 const CXXRecordDecl *BaseDecl = B.getType()->getAsCXXRecordDecl();
1818 CharUnits BaseOffsetInLayoutClass;
1820 if (B.isVirtual()) {
1821 if (!VBases.insert(BaseDecl).second)
1824 const ASTRecordLayout &LayoutClassLayout =
1825 Context.getASTRecordLayout(LayoutClass);
1827 BaseOffsetInLayoutClass =
1828 LayoutClassLayout.getVBaseClassOffset(BaseDecl);
1830 BaseOffsetInLayoutClass =
1831 OffsetInLayoutClass + Layout.getBaseClassOffset(BaseDecl);
1834 DeterminePrimaryVirtualBases(BaseDecl, BaseOffsetInLayoutClass, VBases);
1838 void ItaniumVTableBuilder::LayoutVTablesForVirtualBases(
1839 const CXXRecordDecl *RD, VisitedVirtualBasesSetTy &VBases) {
1840 // Itanium C++ ABI 2.5.2:
1841 // Then come the virtual base virtual tables, also in inheritance graph
1842 // order, and again excluding primary bases (which share virtual tables with
1843 // the classes for which they are primary).
1844 for (const auto &B : RD->bases()) {
1845 const CXXRecordDecl *BaseDecl = B.getType()->getAsCXXRecordDecl();
1847 // Check if this base needs a vtable. (If it's virtual, not a primary base
1848 // of some other class, and we haven't visited it before).
1849 if (B.isVirtual() && BaseDecl->isDynamicClass() &&
1850 !PrimaryVirtualBases.count(BaseDecl) &&
1851 VBases.insert(BaseDecl).second) {
1852 const ASTRecordLayout &MostDerivedClassLayout =
1853 Context.getASTRecordLayout(MostDerivedClass);
1854 CharUnits BaseOffset =
1855 MostDerivedClassLayout.getVBaseClassOffset(BaseDecl);
1857 const ASTRecordLayout &LayoutClassLayout =
1858 Context.getASTRecordLayout(LayoutClass);
1859 CharUnits BaseOffsetInLayoutClass =
1860 LayoutClassLayout.getVBaseClassOffset(BaseDecl);
1862 LayoutPrimaryAndSecondaryVTables(
1863 BaseSubobject(BaseDecl, BaseOffset),
1864 /*BaseIsMorallyVirtual=*/true,
1865 /*BaseIsVirtualInLayoutClass=*/true,
1866 BaseOffsetInLayoutClass);
1869 // We only need to check the base for virtual base vtables if it actually
1870 // has virtual bases.
1871 if (BaseDecl->getNumVBases())
1872 LayoutVTablesForVirtualBases(BaseDecl, VBases);
1876 /// dumpLayout - Dump the vtable layout.
1877 void ItaniumVTableBuilder::dumpLayout(raw_ostream &Out) {
1878 // FIXME: write more tests that actually use the dumpLayout output to prevent
1879 // ItaniumVTableBuilder regressions.
1881 if (isBuildingConstructorVTable()) {
1882 Out << "Construction vtable for ('";
1883 MostDerivedClass->printQualifiedName(Out);
1885 Out << MostDerivedClassOffset.getQuantity() << ") in '";
1886 LayoutClass->printQualifiedName(Out);
1888 Out << "Vtable for '";
1889 MostDerivedClass->printQualifiedName(Out);
1891 Out << "' (" << Components.size() << " entries).\n";
1893 // Iterate through the address points and insert them into a new map where
1894 // they are keyed by the index and not the base object.
1895 // Since an address point can be shared by multiple subobjects, we use an
1897 std::multimap<uint64_t, BaseSubobject> AddressPointsByIndex;
1898 for (const auto &AP : AddressPoints) {
1899 const BaseSubobject &Base = AP.first;
1901 VTableIndices[AP.second.VTableIndex] + AP.second.AddressPointIndex;
1903 AddressPointsByIndex.insert(std::make_pair(Index, Base));
1906 for (unsigned I = 0, E = Components.size(); I != E; ++I) {
1909 Out << llvm::format("%4d | ", I);
1911 const VTableComponent &Component = Components[I];
1913 // Dump the component.
1914 switch (Component.getKind()) {
1916 case VTableComponent::CK_VCallOffset:
1917 Out << "vcall_offset ("
1918 << Component.getVCallOffset().getQuantity()
1922 case VTableComponent::CK_VBaseOffset:
1923 Out << "vbase_offset ("
1924 << Component.getVBaseOffset().getQuantity()
1928 case VTableComponent::CK_OffsetToTop:
1929 Out << "offset_to_top ("
1930 << Component.getOffsetToTop().getQuantity()
1934 case VTableComponent::CK_RTTI:
1935 Component.getRTTIDecl()->printQualifiedName(Out);
1939 case VTableComponent::CK_FunctionPointer: {
1940 const CXXMethodDecl *MD = Component.getFunctionDecl();
1943 PredefinedExpr::ComputeName(PredefinedExpr::PrettyFunctionNoVirtual,
1949 if (MD->isDeleted())
1950 Out << " [deleted]";
1952 ThunkInfo Thunk = VTableThunks.lookup(I);
1953 if (!Thunk.isEmpty()) {
1954 // If this function pointer has a return adjustment, dump it.
1955 if (!Thunk.Return.isEmpty()) {
1956 Out << "\n [return adjustment: ";
1957 Out << Thunk.Return.NonVirtual << " non-virtual";
1959 if (Thunk.Return.Virtual.Itanium.VBaseOffsetOffset) {
1960 Out << ", " << Thunk.Return.Virtual.Itanium.VBaseOffsetOffset;
1961 Out << " vbase offset offset";
1967 // If this function pointer has a 'this' pointer adjustment, dump it.
1968 if (!Thunk.This.isEmpty()) {
1969 Out << "\n [this adjustment: ";
1970 Out << Thunk.This.NonVirtual << " non-virtual";
1972 if (Thunk.This.Virtual.Itanium.VCallOffsetOffset) {
1973 Out << ", " << Thunk.This.Virtual.Itanium.VCallOffsetOffset;
1974 Out << " vcall offset offset";
1984 case VTableComponent::CK_CompleteDtorPointer:
1985 case VTableComponent::CK_DeletingDtorPointer: {
1987 Component.getKind() == VTableComponent::CK_CompleteDtorPointer;
1989 const CXXDestructorDecl *DD = Component.getDestructorDecl();
1991 DD->printQualifiedName(Out);
1993 Out << "() [complete]";
1995 Out << "() [deleting]";
2000 ThunkInfo Thunk = VTableThunks.lookup(I);
2001 if (!Thunk.isEmpty()) {
2002 // If this destructor has a 'this' pointer adjustment, dump it.
2003 if (!Thunk.This.isEmpty()) {
2004 Out << "\n [this adjustment: ";
2005 Out << Thunk.This.NonVirtual << " non-virtual";
2007 if (Thunk.This.Virtual.Itanium.VCallOffsetOffset) {
2008 Out << ", " << Thunk.This.Virtual.Itanium.VCallOffsetOffset;
2009 Out << " vcall offset offset";
2019 case VTableComponent::CK_UnusedFunctionPointer: {
2020 const CXXMethodDecl *MD = Component.getUnusedFunctionDecl();
2023 PredefinedExpr::ComputeName(PredefinedExpr::PrettyFunctionNoVirtual,
2025 Out << "[unused] " << Str;
2034 // Dump the next address point.
2035 uint64_t NextIndex = Index + 1;
2036 if (AddressPointsByIndex.count(NextIndex)) {
2037 if (AddressPointsByIndex.count(NextIndex) == 1) {
2038 const BaseSubobject &Base =
2039 AddressPointsByIndex.find(NextIndex)->second;
2042 Base.getBase()->printQualifiedName(Out);
2043 Out << ", " << Base.getBaseOffset().getQuantity();
2044 Out << ") vtable address --\n";
2046 CharUnits BaseOffset =
2047 AddressPointsByIndex.lower_bound(NextIndex)->second.getBaseOffset();
2049 // We store the class names in a set to get a stable order.
2050 std::set<std::string> ClassNames;
2051 for (const auto &I :
2052 llvm::make_range(AddressPointsByIndex.equal_range(NextIndex))) {
2053 assert(I.second.getBaseOffset() == BaseOffset &&
2054 "Invalid base offset!");
2055 const CXXRecordDecl *RD = I.second.getBase();
2056 ClassNames.insert(RD->getQualifiedNameAsString());
2059 for (const std::string &Name : ClassNames) {
2060 Out << " -- (" << Name;
2061 Out << ", " << BaseOffset.getQuantity() << ") vtable address --\n";
2069 if (isBuildingConstructorVTable())
2072 if (MostDerivedClass->getNumVBases()) {
2073 // We store the virtual base class names and their offsets in a map to get
2076 std::map<std::string, CharUnits> ClassNamesAndOffsets;
2077 for (const auto &I : VBaseOffsetOffsets) {
2078 std::string ClassName = I.first->getQualifiedNameAsString();
2079 CharUnits OffsetOffset = I.second;
2080 ClassNamesAndOffsets.insert(std::make_pair(ClassName, OffsetOffset));
2083 Out << "Virtual base offset offsets for '";
2084 MostDerivedClass->printQualifiedName(Out);
2086 Out << ClassNamesAndOffsets.size();
2087 Out << (ClassNamesAndOffsets.size() == 1 ? " entry" : " entries") << ").\n";
2089 for (const auto &I : ClassNamesAndOffsets)
2090 Out << " " << I.first << " | " << I.second.getQuantity() << '\n';
2095 if (!Thunks.empty()) {
2096 // We store the method names in a map to get a stable order.
2097 std::map<std::string, const CXXMethodDecl *> MethodNamesAndDecls;
2099 for (const auto &I : Thunks) {
2100 const CXXMethodDecl *MD = I.first;
2101 std::string MethodName =
2102 PredefinedExpr::ComputeName(PredefinedExpr::PrettyFunctionNoVirtual,
2105 MethodNamesAndDecls.insert(std::make_pair(MethodName, MD));
2108 for (const auto &I : MethodNamesAndDecls) {
2109 const std::string &MethodName = I.first;
2110 const CXXMethodDecl *MD = I.second;
2112 ThunkInfoVectorTy ThunksVector = Thunks[MD];
2113 std::sort(ThunksVector.begin(), ThunksVector.end(),
2114 [](const ThunkInfo &LHS, const ThunkInfo &RHS) {
2115 assert(LHS.Method == nullptr && RHS.Method == nullptr);
2116 return std::tie(LHS.This, LHS.Return) < std::tie(RHS.This, RHS.Return);
2119 Out << "Thunks for '" << MethodName << "' (" << ThunksVector.size();
2120 Out << (ThunksVector.size() == 1 ? " entry" : " entries") << ").\n";
2122 for (unsigned I = 0, E = ThunksVector.size(); I != E; ++I) {
2123 const ThunkInfo &Thunk = ThunksVector[I];
2125 Out << llvm::format("%4d | ", I);
2127 // If this function pointer has a return pointer adjustment, dump it.
2128 if (!Thunk.Return.isEmpty()) {
2129 Out << "return adjustment: " << Thunk.Return.NonVirtual;
2130 Out << " non-virtual";
2131 if (Thunk.Return.Virtual.Itanium.VBaseOffsetOffset) {
2132 Out << ", " << Thunk.Return.Virtual.Itanium.VBaseOffsetOffset;
2133 Out << " vbase offset offset";
2136 if (!Thunk.This.isEmpty())
2140 // If this function pointer has a 'this' pointer adjustment, dump it.
2141 if (!Thunk.This.isEmpty()) {
2142 Out << "this adjustment: ";
2143 Out << Thunk.This.NonVirtual << " non-virtual";
2145 if (Thunk.This.Virtual.Itanium.VCallOffsetOffset) {
2146 Out << ", " << Thunk.This.Virtual.Itanium.VCallOffsetOffset;
2147 Out << " vcall offset offset";
2158 // Compute the vtable indices for all the member functions.
2159 // Store them in a map keyed by the index so we'll get a sorted table.
2160 std::map<uint64_t, std::string> IndicesMap;
2162 for (const auto *MD : MostDerivedClass->methods()) {
2163 // We only want virtual member functions.
2164 if (!MD->isVirtual())
2166 MD = MD->getCanonicalDecl();
2168 std::string MethodName =
2169 PredefinedExpr::ComputeName(PredefinedExpr::PrettyFunctionNoVirtual,
2172 if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) {
2173 GlobalDecl GD(DD, Dtor_Complete);
2174 assert(MethodVTableIndices.count(GD));
2175 uint64_t VTableIndex = MethodVTableIndices[GD];
2176 IndicesMap[VTableIndex] = MethodName + " [complete]";
2177 IndicesMap[VTableIndex + 1] = MethodName + " [deleting]";
2179 assert(MethodVTableIndices.count(MD));
2180 IndicesMap[MethodVTableIndices[MD]] = MethodName;
2184 // Print the vtable indices for all the member functions.
2185 if (!IndicesMap.empty()) {
2186 Out << "VTable indices for '";
2187 MostDerivedClass->printQualifiedName(Out);
2188 Out << "' (" << IndicesMap.size() << " entries).\n";
2190 for (const auto &I : IndicesMap) {
2191 uint64_t VTableIndex = I.first;
2192 const std::string &MethodName = I.second;
2194 Out << llvm::format("%4" PRIu64 " | ", VTableIndex) << MethodName
2203 VTableLayout::VTableLayout(ArrayRef<size_t> VTableIndices,
2204 ArrayRef<VTableComponent> VTableComponents,
2205 ArrayRef<VTableThunkTy> VTableThunks,
2206 const AddressPointsMapTy &AddressPoints)
2207 : VTableComponents(VTableComponents), VTableThunks(VTableThunks),
2208 AddressPoints(AddressPoints) {
2209 if (VTableIndices.size() <= 1)
2210 assert(VTableIndices.size() == 1 && VTableIndices[0] == 0);
2212 this->VTableIndices = OwningArrayRef<size_t>(VTableIndices);
2214 std::sort(this->VTableThunks.begin(), this->VTableThunks.end(),
2215 [](const VTableLayout::VTableThunkTy &LHS,
2216 const VTableLayout::VTableThunkTy &RHS) {
2217 assert((LHS.first != RHS.first || LHS.second == RHS.second) &&
2218 "Different thunks should have unique indices!");
2219 return LHS.first < RHS.first;
2223 VTableLayout::~VTableLayout() { }
2225 ItaniumVTableContext::ItaniumVTableContext(ASTContext &Context)
2226 : VTableContextBase(/*MS=*/false) {}
2228 ItaniumVTableContext::~ItaniumVTableContext() {}
2230 uint64_t ItaniumVTableContext::getMethodVTableIndex(GlobalDecl GD) {
2231 MethodVTableIndicesTy::iterator I = MethodVTableIndices.find(GD);
2232 if (I != MethodVTableIndices.end())
2235 const CXXRecordDecl *RD = cast<CXXMethodDecl>(GD.getDecl())->getParent();
2237 computeVTableRelatedInformation(RD);
2239 I = MethodVTableIndices.find(GD);
2240 assert(I != MethodVTableIndices.end() && "Did not find index!");
2245 ItaniumVTableContext::getVirtualBaseOffsetOffset(const CXXRecordDecl *RD,
2246 const CXXRecordDecl *VBase) {
2247 ClassPairTy ClassPair(RD, VBase);
2249 VirtualBaseClassOffsetOffsetsMapTy::iterator I =
2250 VirtualBaseClassOffsetOffsets.find(ClassPair);
2251 if (I != VirtualBaseClassOffsetOffsets.end())
2254 VCallAndVBaseOffsetBuilder Builder(RD, RD, /*FinalOverriders=*/nullptr,
2255 BaseSubobject(RD, CharUnits::Zero()),
2256 /*BaseIsVirtual=*/false,
2257 /*OffsetInLayoutClass=*/CharUnits::Zero());
2259 for (const auto &I : Builder.getVBaseOffsetOffsets()) {
2260 // Insert all types.
2261 ClassPairTy ClassPair(RD, I.first);
2263 VirtualBaseClassOffsetOffsets.insert(std::make_pair(ClassPair, I.second));
2266 I = VirtualBaseClassOffsetOffsets.find(ClassPair);
2267 assert(I != VirtualBaseClassOffsetOffsets.end() && "Did not find index!");
2272 static std::unique_ptr<VTableLayout>
2273 CreateVTableLayout(const ItaniumVTableBuilder &Builder) {
2274 SmallVector<VTableLayout::VTableThunkTy, 1>
2275 VTableThunks(Builder.vtable_thunks_begin(), Builder.vtable_thunks_end());
2277 return llvm::make_unique<VTableLayout>(
2278 Builder.VTableIndices, Builder.vtable_components(), VTableThunks,
2279 Builder.getAddressPoints());
2283 ItaniumVTableContext::computeVTableRelatedInformation(const CXXRecordDecl *RD) {
2284 std::unique_ptr<const VTableLayout> &Entry = VTableLayouts[RD];
2286 // Check if we've computed this information before.
2290 ItaniumVTableBuilder Builder(*this, RD, CharUnits::Zero(),
2291 /*MostDerivedClassIsVirtual=*/0, RD);
2292 Entry = CreateVTableLayout(Builder);
2294 MethodVTableIndices.insert(Builder.vtable_indices_begin(),
2295 Builder.vtable_indices_end());
2297 // Add the known thunks.
2298 Thunks.insert(Builder.thunks_begin(), Builder.thunks_end());
2300 // If we don't have the vbase information for this class, insert it.
2301 // getVirtualBaseOffsetOffset will compute it separately without computing
2302 // the rest of the vtable related information.
2303 if (!RD->getNumVBases())
2306 const CXXRecordDecl *VBase =
2307 RD->vbases_begin()->getType()->getAsCXXRecordDecl();
2309 if (VirtualBaseClassOffsetOffsets.count(std::make_pair(RD, VBase)))
2312 for (const auto &I : Builder.getVBaseOffsetOffsets()) {
2313 // Insert all types.
2314 ClassPairTy ClassPair(RD, I.first);
2316 VirtualBaseClassOffsetOffsets.insert(std::make_pair(ClassPair, I.second));
2320 std::unique_ptr<VTableLayout>
2321 ItaniumVTableContext::createConstructionVTableLayout(
2322 const CXXRecordDecl *MostDerivedClass, CharUnits MostDerivedClassOffset,
2323 bool MostDerivedClassIsVirtual, const CXXRecordDecl *LayoutClass) {
2324 ItaniumVTableBuilder Builder(*this, MostDerivedClass, MostDerivedClassOffset,
2325 MostDerivedClassIsVirtual, LayoutClass);
2326 return CreateVTableLayout(Builder);
2331 // Vtables in the Microsoft ABI are different from the Itanium ABI.
2333 // The main differences are:
2334 // 1. Separate vftable and vbtable.
2336 // 2. Each subobject with a vfptr gets its own vftable rather than an address
2337 // point in a single vtable shared between all the subobjects.
2338 // Each vftable is represented by a separate section and virtual calls
2339 // must be done using the vftable which has a slot for the function to be
2342 // 3. Virtual method definitions expect their 'this' parameter to point to the
2343 // first vfptr whose table provides a compatible overridden method. In many
2344 // cases, this permits the original vf-table entry to directly call
2345 // the method instead of passing through a thunk.
2346 // See example before VFTableBuilder::ComputeThisOffset below.
2348 // A compatible overridden method is one which does not have a non-trivial
2349 // covariant-return adjustment.
2351 // The first vfptr is the one with the lowest offset in the complete-object
2352 // layout of the defining class, and the method definition will subtract
2353 // that constant offset from the parameter value to get the real 'this'
2354 // value. Therefore, if the offset isn't really constant (e.g. if a virtual
2355 // function defined in a virtual base is overridden in a more derived
2356 // virtual base and these bases have a reverse order in the complete
2357 // object), the vf-table may require a this-adjustment thunk.
2359 // 4. vftables do not contain new entries for overrides that merely require
2360 // this-adjustment. Together with #3, this keeps vf-tables smaller and
2361 // eliminates the need for this-adjustment thunks in many cases, at the cost
2362 // of often requiring redundant work to adjust the "this" pointer.
2364 // 5. Instead of VTT and constructor vtables, vbtables and vtordisps are used.
2365 // Vtordisps are emitted into the class layout if a class has
2366 // a) a user-defined ctor/dtor
2368 // b) a method overriding a method in a virtual base.
2370 // To get a better understanding of this code,
2371 // you might want to see examples in test/CodeGenCXX/microsoft-abi-vtables-*.cpp
2373 class VFTableBuilder {
2375 typedef MicrosoftVTableContext::MethodVFTableLocation MethodVFTableLocation;
2377 typedef llvm::DenseMap<GlobalDecl, MethodVFTableLocation>
2378 MethodVFTableLocationsTy;
2380 typedef llvm::iterator_range<MethodVFTableLocationsTy::const_iterator>
2381 method_locations_range;
2384 /// VTables - Global vtable information.
2385 MicrosoftVTableContext &VTables;
2387 /// Context - The ASTContext which we will use for layout information.
2388 ASTContext &Context;
2390 /// MostDerivedClass - The most derived class for which we're building this
2392 const CXXRecordDecl *MostDerivedClass;
2394 const ASTRecordLayout &MostDerivedClassLayout;
2396 const VPtrInfo &WhichVFPtr;
2398 /// FinalOverriders - The final overriders of the most derived class.
2399 const FinalOverriders Overriders;
2401 /// Components - The components of the vftable being built.
2402 SmallVector<VTableComponent, 64> Components;
2404 MethodVFTableLocationsTy MethodVFTableLocations;
2406 /// \brief Does this class have an RTTI component?
2407 bool HasRTTIComponent = false;
2409 /// MethodInfo - Contains information about a method in a vtable.
2410 /// (Used for computing 'this' pointer adjustment thunks.
2412 /// VBTableIndex - The nonzero index in the vbtable that
2413 /// this method's base has, or zero.
2414 const uint64_t VBTableIndex;
2416 /// VFTableIndex - The index in the vftable that this method has.
2417 const uint64_t VFTableIndex;
2419 /// Shadowed - Indicates if this vftable slot is shadowed by
2420 /// a slot for a covariant-return override. If so, it shouldn't be printed
2421 /// or used for vcalls in the most derived class.
2424 /// UsesExtraSlot - Indicates if this vftable slot was created because
2425 /// any of the overridden slots required a return adjusting thunk.
2428 MethodInfo(uint64_t VBTableIndex, uint64_t VFTableIndex,
2429 bool UsesExtraSlot = false)
2430 : VBTableIndex(VBTableIndex), VFTableIndex(VFTableIndex),
2431 Shadowed(false), UsesExtraSlot(UsesExtraSlot) {}
2434 : VBTableIndex(0), VFTableIndex(0), Shadowed(false),
2435 UsesExtraSlot(false) {}
2438 typedef llvm::DenseMap<const CXXMethodDecl *, MethodInfo> MethodInfoMapTy;
2440 /// MethodInfoMap - The information for all methods in the vftable we're
2441 /// currently building.
2442 MethodInfoMapTy MethodInfoMap;
2444 typedef llvm::DenseMap<uint64_t, ThunkInfo> VTableThunksMapTy;
2446 /// VTableThunks - The thunks by vftable index in the vftable currently being
2448 VTableThunksMapTy VTableThunks;
2450 typedef SmallVector<ThunkInfo, 1> ThunkInfoVectorTy;
2451 typedef llvm::DenseMap<const CXXMethodDecl *, ThunkInfoVectorTy> ThunksMapTy;
2453 /// Thunks - A map that contains all the thunks needed for all methods in the
2454 /// most derived class for which the vftable is currently being built.
2457 /// AddThunk - Add a thunk for the given method.
2458 void AddThunk(const CXXMethodDecl *MD, const ThunkInfo &Thunk) {
2459 SmallVector<ThunkInfo, 1> &ThunksVector = Thunks[MD];
2461 // Check if we have this thunk already.
2462 if (std::find(ThunksVector.begin(), ThunksVector.end(), Thunk) !=
2466 ThunksVector.push_back(Thunk);
2469 /// ComputeThisOffset - Returns the 'this' argument offset for the given
2470 /// method, relative to the beginning of the MostDerivedClass.
2471 CharUnits ComputeThisOffset(FinalOverriders::OverriderInfo Overrider);
2473 void CalculateVtordispAdjustment(FinalOverriders::OverriderInfo Overrider,
2474 CharUnits ThisOffset, ThisAdjustment &TA);
2476 /// AddMethod - Add a single virtual member function to the vftable
2477 /// components vector.
2478 void AddMethod(const CXXMethodDecl *MD, ThunkInfo TI) {
2479 if (!TI.isEmpty()) {
2480 VTableThunks[Components.size()] = TI;
2483 if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) {
2484 assert(TI.Return.isEmpty() &&
2485 "Destructor can't have return adjustment!");
2486 Components.push_back(VTableComponent::MakeDeletingDtor(DD));
2488 Components.push_back(VTableComponent::MakeFunction(MD));
2492 /// AddMethods - Add the methods of this base subobject and the relevant
2493 /// subbases to the vftable we're currently laying out.
2494 void AddMethods(BaseSubobject Base, unsigned BaseDepth,
2495 const CXXRecordDecl *LastVBase,
2496 BasesSetVectorTy &VisitedBases);
2498 void LayoutVFTable() {
2499 // RTTI data goes before all other entries.
2500 if (HasRTTIComponent)
2501 Components.push_back(VTableComponent::MakeRTTI(MostDerivedClass));
2503 BasesSetVectorTy VisitedBases;
2504 AddMethods(BaseSubobject(MostDerivedClass, CharUnits::Zero()), 0, nullptr,
2506 assert((HasRTTIComponent ? Components.size() - 1 : Components.size()) &&
2507 "vftable can't be empty");
2509 assert(MethodVFTableLocations.empty());
2510 for (const auto &I : MethodInfoMap) {
2511 const CXXMethodDecl *MD = I.first;
2512 const MethodInfo &MI = I.second;
2513 // Skip the methods that the MostDerivedClass didn't override
2514 // and the entries shadowed by return adjusting thunks.
2515 if (MD->getParent() != MostDerivedClass || MI.Shadowed)
2517 MethodVFTableLocation Loc(MI.VBTableIndex, WhichVFPtr.getVBaseWithVPtr(),
2518 WhichVFPtr.NonVirtualOffset, MI.VFTableIndex);
2519 if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) {
2520 MethodVFTableLocations[GlobalDecl(DD, Dtor_Deleting)] = Loc;
2522 MethodVFTableLocations[MD] = Loc;
2528 VFTableBuilder(MicrosoftVTableContext &VTables,
2529 const CXXRecordDecl *MostDerivedClass, const VPtrInfo &Which)
2531 Context(MostDerivedClass->getASTContext()),
2532 MostDerivedClass(MostDerivedClass),
2533 MostDerivedClassLayout(Context.getASTRecordLayout(MostDerivedClass)),
2535 Overriders(MostDerivedClass, CharUnits(), MostDerivedClass) {
2536 // Provide the RTTI component if RTTIData is enabled. If the vftable would
2537 // be available externally, we should not provide the RTTI componenent. It
2538 // is currently impossible to get available externally vftables with either
2539 // dllimport or extern template instantiations, but eventually we may add a
2540 // flag to support additional devirtualization that needs this.
2541 if (Context.getLangOpts().RTTIData)
2542 HasRTTIComponent = true;
2546 if (Context.getLangOpts().DumpVTableLayouts)
2547 dumpLayout(llvm::outs());
2550 uint64_t getNumThunks() const { return Thunks.size(); }
2552 ThunksMapTy::const_iterator thunks_begin() const { return Thunks.begin(); }
2554 ThunksMapTy::const_iterator thunks_end() const { return Thunks.end(); }
2556 method_locations_range vtable_locations() const {
2557 return method_locations_range(MethodVFTableLocations.begin(),
2558 MethodVFTableLocations.end());
2561 ArrayRef<VTableComponent> vtable_components() const { return Components; }
2563 VTableThunksMapTy::const_iterator vtable_thunks_begin() const {
2564 return VTableThunks.begin();
2567 VTableThunksMapTy::const_iterator vtable_thunks_end() const {
2568 return VTableThunks.end();
2571 void dumpLayout(raw_ostream &);
2576 // Let's study one class hierarchy as an example:
2578 // virtual void f();
2582 // struct B : virtual A {
2583 // virtual void f();
2588 // 0 | (A vftable pointer)
2592 // 0 | (B vbtable pointer)
2593 // 4 | struct A (virtual base)
2594 // 4 | (A vftable pointer)
2597 // Let's assume we have a pointer to the A part of an object of dynamic type B:
2602 // In this hierarchy, f() belongs to the vftable of A, so B::f() expects
2603 // "this" parameter to point at the A subobject, which is B+4.
2604 // In the B::f() prologue, it adjusts "this" back to B by subtracting 4,
2605 // performed as a *static* adjustment.
2607 // Interesting thing happens when we alter the relative placement of A and B
2608 // subobjects in a class:
2609 // struct C : virtual B { };
2615 // Respective record layout is:
2616 // 0 | (C vbtable pointer)
2617 // 4 | struct A (virtual base)
2618 // 4 | (A vftable pointer)
2620 // 12 | struct B (virtual base)
2621 // 12 | (B vbtable pointer)
2623 // The final overrider of f() in class C is still B::f(), so B+4 should be
2624 // passed as "this" to that code. However, "a" points at B-8, so the respective
2625 // vftable entry should hold a thunk that adds 12 to the "this" argument before
2626 // performing a tail call to B::f().
2628 // With this example in mind, we can now calculate the 'this' argument offset
2629 // for the given method, relative to the beginning of the MostDerivedClass.
2631 VFTableBuilder::ComputeThisOffset(FinalOverriders::OverriderInfo Overrider) {
2632 BasesSetVectorTy Bases;
2635 // Find the set of least derived bases that define the given method.
2636 OverriddenMethodsSetTy VisitedOverriddenMethods;
2637 auto InitialOverriddenDefinitionCollector = [&](
2638 const CXXMethodDecl *OverriddenMD) {
2639 if (OverriddenMD->size_overridden_methods() == 0)
2640 Bases.insert(OverriddenMD->getParent());
2641 // Don't recurse on this method if we've already collected it.
2642 return VisitedOverriddenMethods.insert(OverriddenMD).second;
2644 visitAllOverriddenMethods(Overrider.Method,
2645 InitialOverriddenDefinitionCollector);
2648 // If there are no overrides then 'this' is located
2649 // in the base that defines the method.
2650 if (Bases.size() == 0)
2651 return Overrider.Offset;
2654 Overrider.Method->getParent()->lookupInBases(
2655 [&Bases](const CXXBaseSpecifier *Specifier, CXXBasePath &) {
2656 return Bases.count(Specifier->getType()->getAsCXXRecordDecl());
2660 // This will hold the smallest this offset among overridees of MD.
2661 // This implies that an offset of a non-virtual base will dominate an offset
2662 // of a virtual base to potentially reduce the number of thunks required
2663 // in the derived classes that inherit this method.
2667 const ASTRecordLayout &OverriderRDLayout =
2668 Context.getASTRecordLayout(Overrider.Method->getParent());
2669 for (const CXXBasePath &Path : Paths) {
2670 CharUnits ThisOffset = Overrider.Offset;
2671 CharUnits LastVBaseOffset;
2673 // For each path from the overrider to the parents of the overridden
2674 // methods, traverse the path, calculating the this offset in the most
2676 for (const CXXBasePathElement &Element : Path) {
2677 QualType CurTy = Element.Base->getType();
2678 const CXXRecordDecl *PrevRD = Element.Class,
2679 *CurRD = CurTy->getAsCXXRecordDecl();
2680 const ASTRecordLayout &Layout = Context.getASTRecordLayout(PrevRD);
2682 if (Element.Base->isVirtual()) {
2683 // The interesting things begin when you have virtual inheritance.
2684 // The final overrider will use a static adjustment equal to the offset
2685 // of the vbase in the final overrider class.
2686 // For example, if the final overrider is in a vbase B of the most
2687 // derived class and it overrides a method of the B's own vbase A,
2688 // it uses A* as "this". In its prologue, it can cast A* to B* with
2689 // a static offset. This offset is used regardless of the actual
2690 // offset of A from B in the most derived class, requiring an
2691 // this-adjusting thunk in the vftable if A and B are laid out
2692 // differently in the most derived class.
2693 LastVBaseOffset = ThisOffset =
2694 Overrider.Offset + OverriderRDLayout.getVBaseClassOffset(CurRD);
2696 ThisOffset += Layout.getBaseClassOffset(CurRD);
2700 if (isa<CXXDestructorDecl>(Overrider.Method)) {
2701 if (LastVBaseOffset.isZero()) {
2702 // If a "Base" class has at least one non-virtual base with a virtual
2703 // destructor, the "Base" virtual destructor will take the address
2704 // of the "Base" subobject as the "this" argument.
2705 ThisOffset = Overrider.Offset;
2707 // A virtual destructor of a virtual base takes the address of the
2708 // virtual base subobject as the "this" argument.
2709 ThisOffset = LastVBaseOffset;
2713 if (Ret > ThisOffset || First) {
2719 assert(!First && "Method not found in the given subobject?");
2723 // Things are getting even more complex when the "this" adjustment has to
2724 // use a dynamic offset instead of a static one, or even two dynamic offsets.
2725 // This is sometimes required when a virtual call happens in the middle of
2726 // a non-most-derived class construction or destruction.
2728 // Let's take a look at the following example:
2730 // virtual void f();
2733 // void foo(A *a) { a->f(); } // Knows nothing about siblings of A.
2735 // struct B : virtual A {
2736 // virtual void f();
2742 // struct C : virtual B {
2743 // virtual void f();
2746 // Record layouts for these classes are:
2748 // 0 | (A vftable pointer)
2751 // 0 | (B vbtable pointer)
2752 // 4 | (vtordisp for vbase A)
2753 // 8 | struct A (virtual base)
2754 // 8 | (A vftable pointer)
2757 // 0 | (C vbtable pointer)
2758 // 4 | (vtordisp for vbase A)
2759 // 8 | struct A (virtual base) // A precedes B!
2760 // 8 | (A vftable pointer)
2761 // 12 | struct B (virtual base)
2762 // 12 | (B vbtable pointer)
2764 // When one creates an object of type C, the C constructor:
2765 // - initializes all the vbptrs, then
2766 // - calls the A subobject constructor
2767 // (initializes A's vfptr with an address of A vftable), then
2768 // - calls the B subobject constructor
2769 // (initializes A's vfptr with an address of B vftable and vtordisp for A),
2770 // that in turn calls foo(), then
2771 // - initializes A's vfptr with an address of C vftable and zeroes out the
2773 // FIXME: if a structor knows it belongs to MDC, why doesn't it use a vftable
2774 // without vtordisp thunks?
2775 // FIXME: how are vtordisp handled in the presence of nooverride/final?
2777 // When foo() is called, an object with a layout of class C has a vftable
2778 // referencing B::f() that assumes a B layout, so the "this" adjustments are
2779 // incorrect, unless an extra adjustment is done. This adjustment is called
2780 // "vtordisp adjustment". Vtordisp basically holds the difference between the
2781 // actual location of a vbase in the layout class and the location assumed by
2782 // the vftable of the class being constructed/destructed. Vtordisp is only
2783 // needed if "this" escapes a
2784 // structor (or we can't prove otherwise).
2785 // [i.e. vtordisp is a dynamic adjustment for a static adjustment, which is an
2786 // estimation of a dynamic adjustment]
2788 // foo() gets a pointer to the A vbase and doesn't know anything about B or C,
2789 // so it just passes that pointer as "this" in a virtual call.
2790 // If there was no vtordisp, that would just dispatch to B::f().
2791 // However, B::f() assumes B+8 is passed as "this",
2792 // yet the pointer foo() passes along is B-4 (i.e. C+8).
2793 // An extra adjustment is needed, so we emit a thunk into the B vftable.
2794 // This vtordisp thunk subtracts the value of vtordisp
2795 // from the "this" argument (-12) before making a tailcall to B::f().
2797 // Let's consider an even more complex example:
2798 // struct D : virtual B, virtual C {
2805 // 0 | (D vbtable pointer)
2806 // 4 | (vtordisp for vbase A)
2807 // 8 | struct A (virtual base) // A precedes both B and C!
2808 // 8 | (A vftable pointer)
2809 // 12 | struct B (virtual base) // B precedes C!
2810 // 12 | (B vbtable pointer)
2811 // 16 | struct C (virtual base)
2812 // 16 | (C vbtable pointer)
2814 // When D::D() calls foo(), we find ourselves in a thunk that should tailcall
2815 // to C::f(), which assumes C+8 as its "this" parameter. This time, foo()
2816 // passes along A, which is C-8. The A vtordisp holds
2817 // "D.vbptr[index_of_A] - offset_of_A_in_D"
2818 // and we statically know offset_of_A_in_D, so can get a pointer to D.
2819 // When we know it, we can make an extra vbtable lookup to locate the C vbase
2820 // and one extra static adjustment to calculate the expected value of C+8.
2821 void VFTableBuilder::CalculateVtordispAdjustment(
2822 FinalOverriders::OverriderInfo Overrider, CharUnits ThisOffset,
2823 ThisAdjustment &TA) {
2824 const ASTRecordLayout::VBaseOffsetsMapTy &VBaseMap =
2825 MostDerivedClassLayout.getVBaseOffsetsMap();
2826 const ASTRecordLayout::VBaseOffsetsMapTy::const_iterator &VBaseMapEntry =
2827 VBaseMap.find(WhichVFPtr.getVBaseWithVPtr());
2828 assert(VBaseMapEntry != VBaseMap.end());
2830 // If there's no vtordisp or the final overrider is defined in the same vbase
2831 // as the initial declaration, we don't need any vtordisp adjustment.
2832 if (!VBaseMapEntry->second.hasVtorDisp() ||
2833 Overrider.VirtualBase == WhichVFPtr.getVBaseWithVPtr())
2836 // OK, now we know we need to use a vtordisp thunk.
2837 // The implicit vtordisp field is located right before the vbase.
2838 CharUnits OffsetOfVBaseWithVFPtr = VBaseMapEntry->second.VBaseOffset;
2839 TA.Virtual.Microsoft.VtordispOffset =
2840 (OffsetOfVBaseWithVFPtr - WhichVFPtr.FullOffsetInMDC).getQuantity() - 4;
2842 // A simple vtordisp thunk will suffice if the final overrider is defined
2843 // in either the most derived class or its non-virtual base.
2844 if (Overrider.Method->getParent() == MostDerivedClass ||
2845 !Overrider.VirtualBase)
2848 // Otherwise, we need to do use the dynamic offset of the final overrider
2849 // in order to get "this" adjustment right.
2850 TA.Virtual.Microsoft.VBPtrOffset =
2851 (OffsetOfVBaseWithVFPtr + WhichVFPtr.NonVirtualOffset -
2852 MostDerivedClassLayout.getVBPtrOffset()).getQuantity();
2853 TA.Virtual.Microsoft.VBOffsetOffset =
2854 Context.getTypeSizeInChars(Context.IntTy).getQuantity() *
2855 VTables.getVBTableIndex(MostDerivedClass, Overrider.VirtualBase);
2857 TA.NonVirtual = (ThisOffset - Overrider.Offset).getQuantity();
2860 static void GroupNewVirtualOverloads(
2861 const CXXRecordDecl *RD,
2862 SmallVector<const CXXMethodDecl *, 10> &VirtualMethods) {
2863 // Put the virtual methods into VirtualMethods in the proper order:
2864 // 1) Group overloads by declaration name. New groups are added to the
2865 // vftable in the order of their first declarations in this class
2866 // (including overrides, non-virtual methods and any other named decl that
2867 // might be nested within the class).
2868 // 2) In each group, new overloads appear in the reverse order of declaration.
2869 typedef SmallVector<const CXXMethodDecl *, 1> MethodGroup;
2870 SmallVector<MethodGroup, 10> Groups;
2871 typedef llvm::DenseMap<DeclarationName, unsigned> VisitedGroupIndicesTy;
2872 VisitedGroupIndicesTy VisitedGroupIndices;
2873 for (const auto *D : RD->decls()) {
2874 const auto *ND = dyn_cast<NamedDecl>(D);
2877 VisitedGroupIndicesTy::iterator J;
2879 std::tie(J, Inserted) = VisitedGroupIndices.insert(
2880 std::make_pair(ND->getDeclName(), Groups.size()));
2882 Groups.push_back(MethodGroup());
2883 if (const auto *MD = dyn_cast<CXXMethodDecl>(ND))
2884 if (MD->isVirtual())
2885 Groups[J->second].push_back(MD->getCanonicalDecl());
2888 for (const MethodGroup &Group : Groups)
2889 VirtualMethods.append(Group.rbegin(), Group.rend());
2892 static bool isDirectVBase(const CXXRecordDecl *Base, const CXXRecordDecl *RD) {
2893 for (const auto &B : RD->bases()) {
2894 if (B.isVirtual() && B.getType()->getAsCXXRecordDecl() == Base)
2900 void VFTableBuilder::AddMethods(BaseSubobject Base, unsigned BaseDepth,
2901 const CXXRecordDecl *LastVBase,
2902 BasesSetVectorTy &VisitedBases) {
2903 const CXXRecordDecl *RD = Base.getBase();
2904 if (!RD->isPolymorphic())
2907 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
2909 // See if this class expands a vftable of the base we look at, which is either
2910 // the one defined by the vfptr base path or the primary base of the current
2912 const CXXRecordDecl *NextBase = nullptr, *NextLastVBase = LastVBase;
2913 CharUnits NextBaseOffset;
2914 if (BaseDepth < WhichVFPtr.PathToIntroducingObject.size()) {
2915 NextBase = WhichVFPtr.PathToIntroducingObject[BaseDepth];
2916 if (isDirectVBase(NextBase, RD)) {
2917 NextLastVBase = NextBase;
2918 NextBaseOffset = MostDerivedClassLayout.getVBaseClassOffset(NextBase);
2921 Base.getBaseOffset() + Layout.getBaseClassOffset(NextBase);
2923 } else if (const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase()) {
2924 assert(!Layout.isPrimaryBaseVirtual() &&
2925 "No primary virtual bases in this ABI");
2926 NextBase = PrimaryBase;
2927 NextBaseOffset = Base.getBaseOffset();
2931 AddMethods(BaseSubobject(NextBase, NextBaseOffset), BaseDepth + 1,
2932 NextLastVBase, VisitedBases);
2933 if (!VisitedBases.insert(NextBase))
2934 llvm_unreachable("Found a duplicate primary base!");
2937 SmallVector<const CXXMethodDecl*, 10> VirtualMethods;
2938 // Put virtual methods in the proper order.
2939 GroupNewVirtualOverloads(RD, VirtualMethods);
2941 // Now go through all virtual member functions and add them to the current
2942 // vftable. This is done by
2943 // - replacing overridden methods in their existing slots, as long as they
2944 // don't require return adjustment; calculating This adjustment if needed.
2945 // - adding new slots for methods of the current base not present in any
2947 // - adding new slots for methods that require Return adjustment.
2948 // We keep track of the methods visited in the sub-bases in MethodInfoMap.
2949 for (const CXXMethodDecl *MD : VirtualMethods) {
2950 FinalOverriders::OverriderInfo FinalOverrider =
2951 Overriders.getOverrider(MD, Base.getBaseOffset());
2952 const CXXMethodDecl *FinalOverriderMD = FinalOverrider.Method;
2953 const CXXMethodDecl *OverriddenMD =
2954 FindNearestOverriddenMethod(MD, VisitedBases);
2956 ThisAdjustment ThisAdjustmentOffset;
2957 bool ReturnAdjustingThunk = false, ForceReturnAdjustmentMangling = false;
2958 CharUnits ThisOffset = ComputeThisOffset(FinalOverrider);
2959 ThisAdjustmentOffset.NonVirtual =
2960 (ThisOffset - WhichVFPtr.FullOffsetInMDC).getQuantity();
2961 if ((OverriddenMD || FinalOverriderMD != MD) &&
2962 WhichVFPtr.getVBaseWithVPtr())
2963 CalculateVtordispAdjustment(FinalOverrider, ThisOffset,
2964 ThisAdjustmentOffset);
2967 // If MD overrides anything in this vftable, we need to update the
2969 MethodInfoMapTy::iterator OverriddenMDIterator =
2970 MethodInfoMap.find(OverriddenMD);
2972 // If the overridden method went to a different vftable, skip it.
2973 if (OverriddenMDIterator == MethodInfoMap.end())
2976 MethodInfo &OverriddenMethodInfo = OverriddenMDIterator->second;
2978 // Let's check if the overrider requires any return adjustments.
2979 // We must create a new slot if the MD's return type is not trivially
2980 // convertible to the OverriddenMD's one.
2981 // Once a chain of method overrides adds a return adjusting vftable slot,
2982 // all subsequent overrides will also use an extra method slot.
2983 ReturnAdjustingThunk = !ComputeReturnAdjustmentBaseOffset(
2984 Context, MD, OverriddenMD).isEmpty() ||
2985 OverriddenMethodInfo.UsesExtraSlot;
2987 if (!ReturnAdjustingThunk) {
2988 // No return adjustment needed - just replace the overridden method info
2989 // with the current info.
2990 MethodInfo MI(OverriddenMethodInfo.VBTableIndex,
2991 OverriddenMethodInfo.VFTableIndex);
2992 MethodInfoMap.erase(OverriddenMDIterator);
2994 assert(!MethodInfoMap.count(MD) &&
2995 "Should not have method info for this method yet!");
2996 MethodInfoMap.insert(std::make_pair(MD, MI));
3000 // In case we need a return adjustment, we'll add a new slot for
3001 // the overrider. Mark the overriden method as shadowed by the new slot.
3002 OverriddenMethodInfo.Shadowed = true;
3004 // Force a special name mangling for a return-adjusting thunk
3005 // unless the method is the final overrider without this adjustment.
3006 ForceReturnAdjustmentMangling =
3007 !(MD == FinalOverriderMD && ThisAdjustmentOffset.isEmpty());
3008 } else if (Base.getBaseOffset() != WhichVFPtr.FullOffsetInMDC ||
3009 MD->size_overridden_methods()) {
3010 // Skip methods that don't belong to the vftable of the current class,
3011 // e.g. each method that wasn't seen in any of the visited sub-bases
3012 // but overrides multiple methods of other sub-bases.
3016 // If we got here, MD is a method not seen in any of the sub-bases or
3017 // it requires return adjustment. Insert the method info for this method.
3019 LastVBase ? VTables.getVBTableIndex(MostDerivedClass, LastVBase) : 0;
3020 MethodInfo MI(VBIndex,
3021 HasRTTIComponent ? Components.size() - 1 : Components.size(),
3022 ReturnAdjustingThunk);
3024 assert(!MethodInfoMap.count(MD) &&
3025 "Should not have method info for this method yet!");
3026 MethodInfoMap.insert(std::make_pair(MD, MI));
3028 // Check if this overrider needs a return adjustment.
3029 // We don't want to do this for pure virtual member functions.
3030 BaseOffset ReturnAdjustmentOffset;
3031 ReturnAdjustment ReturnAdjustment;
3032 if (!FinalOverriderMD->isPure()) {
3033 ReturnAdjustmentOffset =
3034 ComputeReturnAdjustmentBaseOffset(Context, FinalOverriderMD, MD);
3036 if (!ReturnAdjustmentOffset.isEmpty()) {
3037 ForceReturnAdjustmentMangling = true;
3038 ReturnAdjustment.NonVirtual =
3039 ReturnAdjustmentOffset.NonVirtualOffset.getQuantity();
3040 if (ReturnAdjustmentOffset.VirtualBase) {
3041 const ASTRecordLayout &DerivedLayout =
3042 Context.getASTRecordLayout(ReturnAdjustmentOffset.DerivedClass);
3043 ReturnAdjustment.Virtual.Microsoft.VBPtrOffset =
3044 DerivedLayout.getVBPtrOffset().getQuantity();
3045 ReturnAdjustment.Virtual.Microsoft.VBIndex =
3046 VTables.getVBTableIndex(ReturnAdjustmentOffset.DerivedClass,
3047 ReturnAdjustmentOffset.VirtualBase);
3051 AddMethod(FinalOverriderMD,
3052 ThunkInfo(ThisAdjustmentOffset, ReturnAdjustment,
3053 ForceReturnAdjustmentMangling ? MD : nullptr));
3057 static void PrintBasePath(const VPtrInfo::BasePath &Path, raw_ostream &Out) {
3058 for (const CXXRecordDecl *Elem :
3059 llvm::make_range(Path.rbegin(), Path.rend())) {
3061 Elem->printQualifiedName(Out);
3066 static void dumpMicrosoftThunkAdjustment(const ThunkInfo &TI, raw_ostream &Out,
3067 bool ContinueFirstLine) {
3068 const ReturnAdjustment &R = TI.Return;
3069 bool Multiline = false;
3070 const char *LinePrefix = "\n ";
3071 if (!R.isEmpty() || TI.Method) {
3072 if (!ContinueFirstLine)
3074 Out << "[return adjustment (to type '"
3075 << TI.Method->getReturnType().getCanonicalType().getAsString()
3077 if (R.Virtual.Microsoft.VBPtrOffset)
3078 Out << "vbptr at offset " << R.Virtual.Microsoft.VBPtrOffset << ", ";
3079 if (R.Virtual.Microsoft.VBIndex)
3080 Out << "vbase #" << R.Virtual.Microsoft.VBIndex << ", ";
3081 Out << R.NonVirtual << " non-virtual]";
3085 const ThisAdjustment &T = TI.This;
3087 if (Multiline || !ContinueFirstLine)
3089 Out << "[this adjustment: ";
3090 if (!TI.This.Virtual.isEmpty()) {
3091 assert(T.Virtual.Microsoft.VtordispOffset < 0);
3092 Out << "vtordisp at " << T.Virtual.Microsoft.VtordispOffset << ", ";
3093 if (T.Virtual.Microsoft.VBPtrOffset) {
3094 Out << "vbptr at " << T.Virtual.Microsoft.VBPtrOffset
3096 assert(T.Virtual.Microsoft.VBOffsetOffset > 0);
3097 Out << LinePrefix << " vboffset at "
3098 << T.Virtual.Microsoft.VBOffsetOffset << " in the vbtable, ";
3101 Out << T.NonVirtual << " non-virtual]";
3105 void VFTableBuilder::dumpLayout(raw_ostream &Out) {
3106 Out << "VFTable for ";
3107 PrintBasePath(WhichVFPtr.PathToIntroducingObject, Out);
3109 MostDerivedClass->printQualifiedName(Out);
3110 Out << "' (" << Components.size()
3111 << (Components.size() == 1 ? " entry" : " entries") << ").\n";
3113 for (unsigned I = 0, E = Components.size(); I != E; ++I) {
3114 Out << llvm::format("%4d | ", I);
3116 const VTableComponent &Component = Components[I];
3118 // Dump the component.
3119 switch (Component.getKind()) {
3120 case VTableComponent::CK_RTTI:
3121 Component.getRTTIDecl()->printQualifiedName(Out);
3125 case VTableComponent::CK_FunctionPointer: {
3126 const CXXMethodDecl *MD = Component.getFunctionDecl();
3128 // FIXME: Figure out how to print the real thunk type, since they can
3129 // differ in the return type.
3130 std::string Str = PredefinedExpr::ComputeName(
3131 PredefinedExpr::PrettyFunctionNoVirtual, MD);
3136 if (MD->isDeleted())
3137 Out << " [deleted]";
3139 ThunkInfo Thunk = VTableThunks.lookup(I);
3140 if (!Thunk.isEmpty())
3141 dumpMicrosoftThunkAdjustment(Thunk, Out, /*ContinueFirstLine=*/false);
3146 case VTableComponent::CK_DeletingDtorPointer: {
3147 const CXXDestructorDecl *DD = Component.getDestructorDecl();
3149 DD->printQualifiedName(Out);
3150 Out << "() [scalar deleting]";
3155 ThunkInfo Thunk = VTableThunks.lookup(I);
3156 if (!Thunk.isEmpty()) {
3157 assert(Thunk.Return.isEmpty() &&
3158 "No return adjustment needed for destructors!");
3159 dumpMicrosoftThunkAdjustment(Thunk, Out, /*ContinueFirstLine=*/false);
3166 DiagnosticsEngine &Diags = Context.getDiagnostics();
3167 unsigned DiagID = Diags.getCustomDiagID(
3168 DiagnosticsEngine::Error,
3169 "Unexpected vftable component type %0 for component number %1");
3170 Diags.Report(MostDerivedClass->getLocation(), DiagID)
3171 << I << Component.getKind();
3179 if (!Thunks.empty()) {
3180 // We store the method names in a map to get a stable order.
3181 std::map<std::string, const CXXMethodDecl *> MethodNamesAndDecls;
3183 for (const auto &I : Thunks) {
3184 const CXXMethodDecl *MD = I.first;
3185 std::string MethodName = PredefinedExpr::ComputeName(
3186 PredefinedExpr::PrettyFunctionNoVirtual, MD);
3188 MethodNamesAndDecls.insert(std::make_pair(MethodName, MD));
3191 for (const auto &MethodNameAndDecl : MethodNamesAndDecls) {
3192 const std::string &MethodName = MethodNameAndDecl.first;
3193 const CXXMethodDecl *MD = MethodNameAndDecl.second;
3195 ThunkInfoVectorTy ThunksVector = Thunks[MD];
3196 std::stable_sort(ThunksVector.begin(), ThunksVector.end(),
3197 [](const ThunkInfo &LHS, const ThunkInfo &RHS) {
3198 // Keep different thunks with the same adjustments in the order they
3199 // were put into the vector.
3200 return std::tie(LHS.This, LHS.Return) < std::tie(RHS.This, RHS.Return);
3203 Out << "Thunks for '" << MethodName << "' (" << ThunksVector.size();
3204 Out << (ThunksVector.size() == 1 ? " entry" : " entries") << ").\n";
3206 for (unsigned I = 0, E = ThunksVector.size(); I != E; ++I) {
3207 const ThunkInfo &Thunk = ThunksVector[I];
3209 Out << llvm::format("%4d | ", I);
3210 dumpMicrosoftThunkAdjustment(Thunk, Out, /*ContinueFirstLine=*/true);
3221 static bool setsIntersect(const llvm::SmallPtrSet<const CXXRecordDecl *, 4> &A,
3222 ArrayRef<const CXXRecordDecl *> B) {
3223 for (const CXXRecordDecl *Decl : B) {
3230 static bool rebucketPaths(VPtrInfoVector &Paths);
3232 /// Produces MSVC-compatible vbtable data. The symbols produced by this
3233 /// algorithm match those produced by MSVC 2012 and newer, which is different
3236 /// MSVC 2012 appears to minimize the vbtable names using the following
3237 /// algorithm. First, walk the class hierarchy in the usual order, depth first,
3238 /// left to right, to find all of the subobjects which contain a vbptr field.
3239 /// Visiting each class node yields a list of inheritance paths to vbptrs. Each
3240 /// record with a vbptr creates an initially empty path.
3242 /// To combine paths from child nodes, the paths are compared to check for
3243 /// ambiguity. Paths are "ambiguous" if multiple paths have the same set of
3244 /// components in the same order. Each group of ambiguous paths is extended by
3245 /// appending the class of the base from which it came. If the current class
3246 /// node produced an ambiguous path, its path is extended with the current class.
3247 /// After extending paths, MSVC again checks for ambiguity, and extends any
3248 /// ambiguous path which wasn't already extended. Because each node yields an
3249 /// unambiguous set of paths, MSVC doesn't need to extend any path more than once
3250 /// to produce an unambiguous set of paths.
3252 /// TODO: Presumably vftables use the same algorithm.
3253 void MicrosoftVTableContext::computeVTablePaths(bool ForVBTables,
3254 const CXXRecordDecl *RD,
3255 VPtrInfoVector &Paths) {
3256 assert(Paths.empty());
3257 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
3259 // Base case: this subobject has its own vptr.
3260 if (ForVBTables ? Layout.hasOwnVBPtr() : Layout.hasOwnVFPtr())
3261 Paths.push_back(llvm::make_unique<VPtrInfo>(RD));
3263 // Recursive case: get all the vbtables from our bases and remove anything
3264 // that shares a virtual base.
3265 llvm::SmallPtrSet<const CXXRecordDecl*, 4> VBasesSeen;
3266 for (const auto &B : RD->bases()) {
3267 const CXXRecordDecl *Base = B.getType()->getAsCXXRecordDecl();
3268 if (B.isVirtual() && VBasesSeen.count(Base))
3271 if (!Base->isDynamicClass())
3274 const VPtrInfoVector &BasePaths =
3275 ForVBTables ? enumerateVBTables(Base) : getVFPtrOffsets(Base);
3277 for (const std::unique_ptr<VPtrInfo> &BaseInfo : BasePaths) {
3278 // Don't include the path if it goes through a virtual base that we've
3279 // already included.
3280 if (setsIntersect(VBasesSeen, BaseInfo->ContainingVBases))
3283 // Copy the path and adjust it as necessary.
3284 auto P = llvm::make_unique<VPtrInfo>(*BaseInfo);
3286 // We mangle Base into the path if the path would've been ambiguous and it
3287 // wasn't already extended with Base.
3288 if (P->MangledPath.empty() || P->MangledPath.back() != Base)
3289 P->NextBaseToMangle = Base;
3291 // Keep track of which vtable the derived class is going to extend with
3292 // new methods or bases. We append to either the vftable of our primary
3293 // base, or the first non-virtual base that has a vbtable.
3294 if (P->ObjectWithVPtr == Base &&
3295 Base == (ForVBTables ? Layout.getBaseSharingVBPtr()
3296 : Layout.getPrimaryBase()))
3297 P->ObjectWithVPtr = RD;
3299 // Keep track of the full adjustment from the MDC to this vtable. The
3300 // adjustment is captured by an optional vbase and a non-virtual offset.
3302 P->ContainingVBases.push_back(Base);
3303 else if (P->ContainingVBases.empty())
3304 P->NonVirtualOffset += Layout.getBaseClassOffset(Base);
3306 // Update the full offset in the MDC.
3307 P->FullOffsetInMDC = P->NonVirtualOffset;
3308 if (const CXXRecordDecl *VB = P->getVBaseWithVPtr())
3309 P->FullOffsetInMDC += Layout.getVBaseClassOffset(VB);
3311 Paths.push_back(std::move(P));
3315 VBasesSeen.insert(Base);
3317 // After visiting any direct base, we've transitively visited all of its
3318 // morally virtual bases.
3319 for (const auto &VB : Base->vbases())
3320 VBasesSeen.insert(VB.getType()->getAsCXXRecordDecl());
3323 // Sort the paths into buckets, and if any of them are ambiguous, extend all
3324 // paths in ambiguous buckets.
3325 bool Changed = true;
3327 Changed = rebucketPaths(Paths);
3330 static bool extendPath(VPtrInfo &P) {
3331 if (P.NextBaseToMangle) {
3332 P.MangledPath.push_back(P.NextBaseToMangle);
3333 P.NextBaseToMangle = nullptr;// Prevent the path from being extended twice.
3339 static bool rebucketPaths(VPtrInfoVector &Paths) {
3340 // What we're essentially doing here is bucketing together ambiguous paths.
3341 // Any bucket with more than one path in it gets extended by NextBase, which
3342 // is usually the direct base of the inherited the vbptr. This code uses a
3343 // sorted vector to implement a multiset to form the buckets. Note that the
3344 // ordering is based on pointers, but it doesn't change our output order. The
3345 // current algorithm is designed to match MSVC 2012's names.
3346 llvm::SmallVector<std::reference_wrapper<VPtrInfo>, 2> PathsSorted;
3347 PathsSorted.reserve(Paths.size());
3348 for (auto& P : Paths)
3349 PathsSorted.push_back(*P);
3350 std::sort(PathsSorted.begin(), PathsSorted.end(),
3351 [](const VPtrInfo &LHS, const VPtrInfo &RHS) {
3352 return LHS.MangledPath < RHS.MangledPath;
3354 bool Changed = false;
3355 for (size_t I = 0, E = PathsSorted.size(); I != E;) {
3356 // Scan forward to find the end of the bucket.
3357 size_t BucketStart = I;
3361 PathsSorted[BucketStart].get().MangledPath ==
3362 PathsSorted[I].get().MangledPath);
3364 // If this bucket has multiple paths, extend them all.
3365 if (I - BucketStart > 1) {
3366 for (size_t II = BucketStart; II != I; ++II)
3367 Changed |= extendPath(PathsSorted[II]);
3368 assert(Changed && "no paths were extended to fix ambiguity");
3374 MicrosoftVTableContext::~MicrosoftVTableContext() {}
3377 typedef llvm::SetVector<BaseSubobject, std::vector<BaseSubobject>,
3378 llvm::DenseSet<BaseSubobject>> FullPathTy;
3381 // This recursive function finds all paths from a subobject centered at
3382 // (RD, Offset) to the subobject located at IntroducingObject.
3383 static void findPathsToSubobject(ASTContext &Context,
3384 const ASTRecordLayout &MostDerivedLayout,
3385 const CXXRecordDecl *RD, CharUnits Offset,
3386 BaseSubobject IntroducingObject,
3387 FullPathTy &FullPath,
3388 std::list<FullPathTy> &Paths) {
3389 if (BaseSubobject(RD, Offset) == IntroducingObject) {
3390 Paths.push_back(FullPath);
3394 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
3396 for (const CXXBaseSpecifier &BS : RD->bases()) {
3397 const CXXRecordDecl *Base = BS.getType()->getAsCXXRecordDecl();
3398 CharUnits NewOffset = BS.isVirtual()
3399 ? MostDerivedLayout.getVBaseClassOffset(Base)
3400 : Offset + Layout.getBaseClassOffset(Base);
3401 FullPath.insert(BaseSubobject(Base, NewOffset));
3402 findPathsToSubobject(Context, MostDerivedLayout, Base, NewOffset,
3403 IntroducingObject, FullPath, Paths);
3404 FullPath.pop_back();
3408 // Return the paths which are not subsets of other paths.
3409 static void removeRedundantPaths(std::list<FullPathTy> &FullPaths) {
3410 FullPaths.remove_if([&](const FullPathTy &SpecificPath) {
3411 for (const FullPathTy &OtherPath : FullPaths) {
3412 if (&SpecificPath == &OtherPath)
3414 if (std::all_of(SpecificPath.begin(), SpecificPath.end(),
3415 [&](const BaseSubobject &BSO) {
3416 return OtherPath.count(BSO) != 0;
3425 static CharUnits getOffsetOfFullPath(ASTContext &Context,
3426 const CXXRecordDecl *RD,
3427 const FullPathTy &FullPath) {
3428 const ASTRecordLayout &MostDerivedLayout =
3429 Context.getASTRecordLayout(RD);
3430 CharUnits Offset = CharUnits::fromQuantity(-1);
3431 for (const BaseSubobject &BSO : FullPath) {
3432 const CXXRecordDecl *Base = BSO.getBase();
3433 // The first entry in the path is always the most derived record, skip it.
3435 assert(Offset.getQuantity() == -1);
3436 Offset = CharUnits::Zero();
3439 assert(Offset.getQuantity() != -1);
3440 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
3441 // While we know which base has to be traversed, we don't know if that base
3442 // was a virtual base.
3443 const CXXBaseSpecifier *BaseBS = std::find_if(
3444 RD->bases_begin(), RD->bases_end(), [&](const CXXBaseSpecifier &BS) {
3445 return BS.getType()->getAsCXXRecordDecl() == Base;
3447 Offset = BaseBS->isVirtual() ? MostDerivedLayout.getVBaseClassOffset(Base)
3448 : Offset + Layout.getBaseClassOffset(Base);
3454 // We want to select the path which introduces the most covariant overrides. If
3455 // two paths introduce overrides which the other path doesn't contain, issue a
3457 static const FullPathTy *selectBestPath(ASTContext &Context,
3458 const CXXRecordDecl *RD,
3459 const VPtrInfo &Info,
3460 std::list<FullPathTy> &FullPaths) {
3461 // Handle some easy cases first.
3462 if (FullPaths.empty())
3464 if (FullPaths.size() == 1)
3465 return &FullPaths.front();
3467 const FullPathTy *BestPath = nullptr;
3468 typedef std::set<const CXXMethodDecl *> OverriderSetTy;
3469 OverriderSetTy LastOverrides;
3470 for (const FullPathTy &SpecificPath : FullPaths) {
3471 assert(!SpecificPath.empty());
3472 OverriderSetTy CurrentOverrides;
3473 const CXXRecordDecl *TopLevelRD = SpecificPath.begin()->getBase();
3474 // Find the distance from the start of the path to the subobject with the
3476 CharUnits BaseOffset =
3477 getOffsetOfFullPath(Context, TopLevelRD, SpecificPath);
3478 FinalOverriders Overriders(TopLevelRD, CharUnits::Zero(), TopLevelRD);
3479 for (const CXXMethodDecl *MD : Info.IntroducingObject->methods()) {
3480 if (!MD->isVirtual())
3482 FinalOverriders::OverriderInfo OI =
3483 Overriders.getOverrider(MD->getCanonicalDecl(), BaseOffset);
3484 const CXXMethodDecl *OverridingMethod = OI.Method;
3485 // Only overriders which have a return adjustment introduce problematic
3487 if (ComputeReturnAdjustmentBaseOffset(Context, OverridingMethod, MD)
3490 // It's possible that the overrider isn't in this path. If so, skip it
3491 // because this path didn't introduce it.
3492 const CXXRecordDecl *OverridingParent = OverridingMethod->getParent();
3493 if (std::none_of(SpecificPath.begin(), SpecificPath.end(),
3494 [&](const BaseSubobject &BSO) {
3495 return BSO.getBase() == OverridingParent;
3498 CurrentOverrides.insert(OverridingMethod);
3500 OverriderSetTy NewOverrides =
3501 llvm::set_difference(CurrentOverrides, LastOverrides);
3502 if (NewOverrides.empty())
3504 OverriderSetTy MissingOverrides =
3505 llvm::set_difference(LastOverrides, CurrentOverrides);
3506 if (MissingOverrides.empty()) {
3507 // This path is a strict improvement over the last path, let's use it.
3508 BestPath = &SpecificPath;
3509 std::swap(CurrentOverrides, LastOverrides);
3511 // This path introduces an overrider with a conflicting covariant thunk.
3512 DiagnosticsEngine &Diags = Context.getDiagnostics();
3513 const CXXMethodDecl *CovariantMD = *NewOverrides.begin();
3514 const CXXMethodDecl *ConflictMD = *MissingOverrides.begin();
3515 Diags.Report(RD->getLocation(), diag::err_vftable_ambiguous_component)
3517 Diags.Report(CovariantMD->getLocation(), diag::note_covariant_thunk)
3519 Diags.Report(ConflictMD->getLocation(), diag::note_covariant_thunk)
3523 // Go with the path that introduced the most covariant overrides. If there is
3524 // no such path, pick the first path.
3525 return BestPath ? BestPath : &FullPaths.front();
3528 static void computeFullPathsForVFTables(ASTContext &Context,
3529 const CXXRecordDecl *RD,
3530 VPtrInfoVector &Paths) {
3531 const ASTRecordLayout &MostDerivedLayout = Context.getASTRecordLayout(RD);
3532 FullPathTy FullPath;
3533 std::list<FullPathTy> FullPaths;
3534 for (const std::unique_ptr<VPtrInfo>& Info : Paths) {
3535 findPathsToSubobject(
3536 Context, MostDerivedLayout, RD, CharUnits::Zero(),
3537 BaseSubobject(Info->IntroducingObject, Info->FullOffsetInMDC), FullPath,
3540 removeRedundantPaths(FullPaths);
3541 Info->PathToIntroducingObject.clear();
3542 if (const FullPathTy *BestPath =
3543 selectBestPath(Context, RD, *Info, FullPaths))
3544 for (const BaseSubobject &BSO : *BestPath)
3545 Info->PathToIntroducingObject.push_back(BSO.getBase());
3550 void MicrosoftVTableContext::computeVTableRelatedInformation(
3551 const CXXRecordDecl *RD) {
3552 assert(RD->isDynamicClass());
3554 // Check if we've computed this information before.
3555 if (VFPtrLocations.count(RD))
3558 const VTableLayout::AddressPointsMapTy EmptyAddressPointsMap;
3561 VPtrInfoVector VFPtrs;
3562 computeVTablePaths(/*ForVBTables=*/false, RD, VFPtrs);
3563 computeFullPathsForVFTables(Context, RD, VFPtrs);
3564 VFPtrLocations[RD] = std::move(VFPtrs);
3567 MethodVFTableLocationsTy NewMethodLocations;
3568 for (const std::unique_ptr<VPtrInfo> &VFPtr : VFPtrLocations[RD]) {
3569 VFTableBuilder Builder(*this, RD, *VFPtr);
3571 VFTableIdTy id(RD, VFPtr->FullOffsetInMDC);
3572 assert(VFTableLayouts.count(id) == 0);
3573 SmallVector<VTableLayout::VTableThunkTy, 1> VTableThunks(
3574 Builder.vtable_thunks_begin(), Builder.vtable_thunks_end());
3575 VFTableLayouts[id] = llvm::make_unique<VTableLayout>(
3576 ArrayRef<size_t>{0}, Builder.vtable_components(), VTableThunks,
3577 EmptyAddressPointsMap);
3578 Thunks.insert(Builder.thunks_begin(), Builder.thunks_end());
3580 for (const auto &Loc : Builder.vtable_locations()) {
3581 GlobalDecl GD = Loc.first;
3582 MethodVFTableLocation NewLoc = Loc.second;
3583 auto M = NewMethodLocations.find(GD);
3584 if (M == NewMethodLocations.end() || NewLoc < M->second)
3585 NewMethodLocations[GD] = NewLoc;
3589 MethodVFTableLocations.insert(NewMethodLocations.begin(),
3590 NewMethodLocations.end());
3591 if (Context.getLangOpts().DumpVTableLayouts)
3592 dumpMethodLocations(RD, NewMethodLocations, llvm::outs());
3595 void MicrosoftVTableContext::dumpMethodLocations(
3596 const CXXRecordDecl *RD, const MethodVFTableLocationsTy &NewMethods,
3598 // Compute the vtable indices for all the member functions.
3599 // Store them in a map keyed by the location so we'll get a sorted table.
3600 std::map<MethodVFTableLocation, std::string> IndicesMap;
3601 bool HasNonzeroOffset = false;
3603 for (const auto &I : NewMethods) {
3604 const CXXMethodDecl *MD = cast<const CXXMethodDecl>(I.first.getDecl());
3605 assert(MD->isVirtual());
3607 std::string MethodName = PredefinedExpr::ComputeName(
3608 PredefinedExpr::PrettyFunctionNoVirtual, MD);
3610 if (isa<CXXDestructorDecl>(MD)) {
3611 IndicesMap[I.second] = MethodName + " [scalar deleting]";
3613 IndicesMap[I.second] = MethodName;
3616 if (!I.second.VFPtrOffset.isZero() || I.second.VBTableIndex != 0)
3617 HasNonzeroOffset = true;
3620 // Print the vtable indices for all the member functions.
3621 if (!IndicesMap.empty()) {
3622 Out << "VFTable indices for ";
3624 RD->printQualifiedName(Out);
3625 Out << "' (" << IndicesMap.size()
3626 << (IndicesMap.size() == 1 ? " entry" : " entries") << ").\n";
3628 CharUnits LastVFPtrOffset = CharUnits::fromQuantity(-1);
3629 uint64_t LastVBIndex = 0;
3630 for (const auto &I : IndicesMap) {
3631 CharUnits VFPtrOffset = I.first.VFPtrOffset;
3632 uint64_t VBIndex = I.first.VBTableIndex;
3633 if (HasNonzeroOffset &&
3634 (VFPtrOffset != LastVFPtrOffset || VBIndex != LastVBIndex)) {
3635 assert(VBIndex > LastVBIndex || VFPtrOffset > LastVFPtrOffset);
3636 Out << " -- accessible via ";
3638 Out << "vbtable index " << VBIndex << ", ";
3639 Out << "vfptr at offset " << VFPtrOffset.getQuantity() << " --\n";
3640 LastVFPtrOffset = VFPtrOffset;
3641 LastVBIndex = VBIndex;
3644 uint64_t VTableIndex = I.first.Index;
3645 const std::string &MethodName = I.second;
3646 Out << llvm::format("%4" PRIu64 " | ", VTableIndex) << MethodName << '\n';
3654 const VirtualBaseInfo &MicrosoftVTableContext::computeVBTableRelatedInformation(
3655 const CXXRecordDecl *RD) {
3656 VirtualBaseInfo *VBI;
3659 // Get or create a VBI for RD. Don't hold a reference to the DenseMap cell,
3660 // as it may be modified and rehashed under us.
3661 std::unique_ptr<VirtualBaseInfo> &Entry = VBaseInfo[RD];
3664 Entry = llvm::make_unique<VirtualBaseInfo>();
3668 computeVTablePaths(/*ForVBTables=*/true, RD, VBI->VBPtrPaths);
3670 // First, see if the Derived class shared the vbptr with a non-virtual base.
3671 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
3672 if (const CXXRecordDecl *VBPtrBase = Layout.getBaseSharingVBPtr()) {
3673 // If the Derived class shares the vbptr with a non-virtual base, the shared
3674 // virtual bases come first so that the layout is the same.
3675 const VirtualBaseInfo &BaseInfo =
3676 computeVBTableRelatedInformation(VBPtrBase);
3677 VBI->VBTableIndices.insert(BaseInfo.VBTableIndices.begin(),
3678 BaseInfo.VBTableIndices.end());
3681 // New vbases are added to the end of the vbtable.
3682 // Skip the self entry and vbases visited in the non-virtual base, if any.
3683 unsigned VBTableIndex = 1 + VBI->VBTableIndices.size();
3684 for (const auto &VB : RD->vbases()) {
3685 const CXXRecordDecl *CurVBase = VB.getType()->getAsCXXRecordDecl();
3686 if (!VBI->VBTableIndices.count(CurVBase))
3687 VBI->VBTableIndices[CurVBase] = VBTableIndex++;
3693 unsigned MicrosoftVTableContext::getVBTableIndex(const CXXRecordDecl *Derived,
3694 const CXXRecordDecl *VBase) {
3695 const VirtualBaseInfo &VBInfo = computeVBTableRelatedInformation(Derived);
3696 assert(VBInfo.VBTableIndices.count(VBase));
3697 return VBInfo.VBTableIndices.find(VBase)->second;
3700 const VPtrInfoVector &
3701 MicrosoftVTableContext::enumerateVBTables(const CXXRecordDecl *RD) {
3702 return computeVBTableRelatedInformation(RD).VBPtrPaths;
3705 const VPtrInfoVector &
3706 MicrosoftVTableContext::getVFPtrOffsets(const CXXRecordDecl *RD) {
3707 computeVTableRelatedInformation(RD);
3709 assert(VFPtrLocations.count(RD) && "Couldn't find vfptr locations");
3710 return VFPtrLocations[RD];
3713 const VTableLayout &
3714 MicrosoftVTableContext::getVFTableLayout(const CXXRecordDecl *RD,
3715 CharUnits VFPtrOffset) {
3716 computeVTableRelatedInformation(RD);
3718 VFTableIdTy id(RD, VFPtrOffset);
3719 assert(VFTableLayouts.count(id) && "Couldn't find a VFTable at this offset");
3720 return *VFTableLayouts[id];
3723 const MicrosoftVTableContext::MethodVFTableLocation &
3724 MicrosoftVTableContext::getMethodVFTableLocation(GlobalDecl GD) {
3725 assert(cast<CXXMethodDecl>(GD.getDecl())->isVirtual() &&
3726 "Only use this method for virtual methods or dtors");
3727 if (isa<CXXDestructorDecl>(GD.getDecl()))
3728 assert(GD.getDtorType() == Dtor_Deleting);
3730 MethodVFTableLocationsTy::iterator I = MethodVFTableLocations.find(GD);
3731 if (I != MethodVFTableLocations.end())
3734 const CXXRecordDecl *RD = cast<CXXMethodDecl>(GD.getDecl())->getParent();
3736 computeVTableRelatedInformation(RD);
3738 I = MethodVFTableLocations.find(GD);
3739 assert(I != MethodVFTableLocations.end() && "Did not find index!");