xref: /freebsd/contrib/llvm-project/clang/lib/Serialization/ASTWriterDecl.cpp (revision 96190b4fef3b4a0cc3ca0606b0c4e3e69a5e6717)
1 //===--- ASTWriterDecl.cpp - Declaration Serialization --------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 //  This file implements serialization for Declarations.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "ASTCommon.h"
14 #include "clang/AST/Attr.h"
15 #include "clang/AST/DeclCXX.h"
16 #include "clang/AST/DeclTemplate.h"
17 #include "clang/AST/DeclVisitor.h"
18 #include "clang/AST/Expr.h"
19 #include "clang/AST/OpenMPClause.h"
20 #include "clang/AST/PrettyDeclStackTrace.h"
21 #include "clang/Basic/SourceManager.h"
22 #include "clang/Serialization/ASTReader.h"
23 #include "clang/Serialization/ASTRecordWriter.h"
24 #include "llvm/Bitstream/BitstreamWriter.h"
25 #include "llvm/Support/ErrorHandling.h"
26 #include <optional>
27 using namespace clang;
28 using namespace serialization;
29 
30 //===----------------------------------------------------------------------===//
31 // Declaration serialization
32 //===----------------------------------------------------------------------===//
33 
34 namespace clang {
35   class ASTDeclWriter : public DeclVisitor<ASTDeclWriter, void> {
36     ASTWriter &Writer;
37     ASTContext &Context;
38     ASTRecordWriter Record;
39 
40     serialization::DeclCode Code;
41     unsigned AbbrevToUse;
42 
43   public:
44     ASTDeclWriter(ASTWriter &Writer, ASTContext &Context,
45                   ASTWriter::RecordDataImpl &Record)
46         : Writer(Writer), Context(Context), Record(Writer, Record),
47           Code((serialization::DeclCode)0), AbbrevToUse(0) {}
48 
49     uint64_t Emit(Decl *D) {
50       if (!Code)
51         llvm::report_fatal_error(StringRef("unexpected declaration kind '") +
52             D->getDeclKindName() + "'");
53       return Record.Emit(Code, AbbrevToUse);
54     }
55 
56     void Visit(Decl *D);
57 
58     void VisitDecl(Decl *D);
59     void VisitPragmaCommentDecl(PragmaCommentDecl *D);
60     void VisitPragmaDetectMismatchDecl(PragmaDetectMismatchDecl *D);
61     void VisitTranslationUnitDecl(TranslationUnitDecl *D);
62     void VisitNamedDecl(NamedDecl *D);
63     void VisitLabelDecl(LabelDecl *LD);
64     void VisitNamespaceDecl(NamespaceDecl *D);
65     void VisitUsingDirectiveDecl(UsingDirectiveDecl *D);
66     void VisitNamespaceAliasDecl(NamespaceAliasDecl *D);
67     void VisitTypeDecl(TypeDecl *D);
68     void VisitTypedefNameDecl(TypedefNameDecl *D);
69     void VisitTypedefDecl(TypedefDecl *D);
70     void VisitTypeAliasDecl(TypeAliasDecl *D);
71     void VisitUnresolvedUsingTypenameDecl(UnresolvedUsingTypenameDecl *D);
72     void VisitUnresolvedUsingIfExistsDecl(UnresolvedUsingIfExistsDecl *D);
73     void VisitTagDecl(TagDecl *D);
74     void VisitEnumDecl(EnumDecl *D);
75     void VisitRecordDecl(RecordDecl *D);
76     void VisitCXXRecordDecl(CXXRecordDecl *D);
77     void VisitClassTemplateSpecializationDecl(
78                                             ClassTemplateSpecializationDecl *D);
79     void VisitClassTemplatePartialSpecializationDecl(
80                                      ClassTemplatePartialSpecializationDecl *D);
81     void VisitVarTemplateSpecializationDecl(VarTemplateSpecializationDecl *D);
82     void VisitVarTemplatePartialSpecializationDecl(
83         VarTemplatePartialSpecializationDecl *D);
84     void VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D);
85     void VisitValueDecl(ValueDecl *D);
86     void VisitEnumConstantDecl(EnumConstantDecl *D);
87     void VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D);
88     void VisitDeclaratorDecl(DeclaratorDecl *D);
89     void VisitFunctionDecl(FunctionDecl *D);
90     void VisitCXXDeductionGuideDecl(CXXDeductionGuideDecl *D);
91     void VisitCXXMethodDecl(CXXMethodDecl *D);
92     void VisitCXXConstructorDecl(CXXConstructorDecl *D);
93     void VisitCXXDestructorDecl(CXXDestructorDecl *D);
94     void VisitCXXConversionDecl(CXXConversionDecl *D);
95     void VisitFieldDecl(FieldDecl *D);
96     void VisitMSPropertyDecl(MSPropertyDecl *D);
97     void VisitMSGuidDecl(MSGuidDecl *D);
98     void VisitUnnamedGlobalConstantDecl(UnnamedGlobalConstantDecl *D);
99     void VisitTemplateParamObjectDecl(TemplateParamObjectDecl *D);
100     void VisitIndirectFieldDecl(IndirectFieldDecl *D);
101     void VisitVarDecl(VarDecl *D);
102     void VisitImplicitParamDecl(ImplicitParamDecl *D);
103     void VisitParmVarDecl(ParmVarDecl *D);
104     void VisitDecompositionDecl(DecompositionDecl *D);
105     void VisitBindingDecl(BindingDecl *D);
106     void VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D);
107     void VisitTemplateDecl(TemplateDecl *D);
108     void VisitConceptDecl(ConceptDecl *D);
109     void VisitImplicitConceptSpecializationDecl(
110         ImplicitConceptSpecializationDecl *D);
111     void VisitRequiresExprBodyDecl(RequiresExprBodyDecl *D);
112     void VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D);
113     void VisitClassTemplateDecl(ClassTemplateDecl *D);
114     void VisitVarTemplateDecl(VarTemplateDecl *D);
115     void VisitFunctionTemplateDecl(FunctionTemplateDecl *D);
116     void VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D);
117     void VisitTypeAliasTemplateDecl(TypeAliasTemplateDecl *D);
118     void VisitUsingDecl(UsingDecl *D);
119     void VisitUsingEnumDecl(UsingEnumDecl *D);
120     void VisitUsingPackDecl(UsingPackDecl *D);
121     void VisitUsingShadowDecl(UsingShadowDecl *D);
122     void VisitConstructorUsingShadowDecl(ConstructorUsingShadowDecl *D);
123     void VisitLinkageSpecDecl(LinkageSpecDecl *D);
124     void VisitExportDecl(ExportDecl *D);
125     void VisitFileScopeAsmDecl(FileScopeAsmDecl *D);
126     void VisitTopLevelStmtDecl(TopLevelStmtDecl *D);
127     void VisitImportDecl(ImportDecl *D);
128     void VisitAccessSpecDecl(AccessSpecDecl *D);
129     void VisitFriendDecl(FriendDecl *D);
130     void VisitFriendTemplateDecl(FriendTemplateDecl *D);
131     void VisitStaticAssertDecl(StaticAssertDecl *D);
132     void VisitBlockDecl(BlockDecl *D);
133     void VisitCapturedDecl(CapturedDecl *D);
134     void VisitEmptyDecl(EmptyDecl *D);
135     void VisitLifetimeExtendedTemporaryDecl(LifetimeExtendedTemporaryDecl *D);
136     void VisitDeclContext(DeclContext *DC);
137     template <typename T> void VisitRedeclarable(Redeclarable<T> *D);
138     void VisitHLSLBufferDecl(HLSLBufferDecl *D);
139 
140     // FIXME: Put in the same order is DeclNodes.td?
141     void VisitObjCMethodDecl(ObjCMethodDecl *D);
142     void VisitObjCTypeParamDecl(ObjCTypeParamDecl *D);
143     void VisitObjCContainerDecl(ObjCContainerDecl *D);
144     void VisitObjCInterfaceDecl(ObjCInterfaceDecl *D);
145     void VisitObjCIvarDecl(ObjCIvarDecl *D);
146     void VisitObjCProtocolDecl(ObjCProtocolDecl *D);
147     void VisitObjCAtDefsFieldDecl(ObjCAtDefsFieldDecl *D);
148     void VisitObjCCategoryDecl(ObjCCategoryDecl *D);
149     void VisitObjCImplDecl(ObjCImplDecl *D);
150     void VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D);
151     void VisitObjCImplementationDecl(ObjCImplementationDecl *D);
152     void VisitObjCCompatibleAliasDecl(ObjCCompatibleAliasDecl *D);
153     void VisitObjCPropertyDecl(ObjCPropertyDecl *D);
154     void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
155     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
156     void VisitOMPAllocateDecl(OMPAllocateDecl *D);
157     void VisitOMPRequiresDecl(OMPRequiresDecl *D);
158     void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
159     void VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D);
160     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
161 
162     /// Add an Objective-C type parameter list to the given record.
163     void AddObjCTypeParamList(ObjCTypeParamList *typeParams) {
164       // Empty type parameter list.
165       if (!typeParams) {
166         Record.push_back(0);
167         return;
168       }
169 
170       Record.push_back(typeParams->size());
171       for (auto *typeParam : *typeParams) {
172         Record.AddDeclRef(typeParam);
173       }
174       Record.AddSourceLocation(typeParams->getLAngleLoc());
175       Record.AddSourceLocation(typeParams->getRAngleLoc());
176     }
177 
178     /// Add to the record the first declaration from each module file that
179     /// provides a declaration of D. The intent is to provide a sufficient
180     /// set such that reloading this set will load all current redeclarations.
181     void AddFirstDeclFromEachModule(const Decl *D, bool IncludeLocal) {
182       llvm::MapVector<ModuleFile*, const Decl*> Firsts;
183       // FIXME: We can skip entries that we know are implied by others.
184       for (const Decl *R = D->getMostRecentDecl(); R; R = R->getPreviousDecl()) {
185         if (R->isFromASTFile())
186           Firsts[Writer.Chain->getOwningModuleFile(R)] = R;
187         else if (IncludeLocal)
188           Firsts[nullptr] = R;
189       }
190       for (const auto &F : Firsts)
191         Record.AddDeclRef(F.second);
192     }
193 
194     /// Get the specialization decl from an entry in the specialization list.
195     template <typename EntryType>
196     typename RedeclarableTemplateDecl::SpecEntryTraits<EntryType>::DeclType *
197     getSpecializationDecl(EntryType &T) {
198       return RedeclarableTemplateDecl::SpecEntryTraits<EntryType>::getDecl(&T);
199     }
200 
201     /// Get the list of partial specializations from a template's common ptr.
202     template<typename T>
203     decltype(T::PartialSpecializations) &getPartialSpecializations(T *Common) {
204       return Common->PartialSpecializations;
205     }
206     ArrayRef<Decl> getPartialSpecializations(FunctionTemplateDecl::Common *) {
207       return std::nullopt;
208     }
209 
210     template<typename DeclTy>
211     void AddTemplateSpecializations(DeclTy *D) {
212       auto *Common = D->getCommonPtr();
213 
214       // If we have any lazy specializations, and the external AST source is
215       // our chained AST reader, we can just write out the DeclIDs. Otherwise,
216       // we need to resolve them to actual declarations.
217       if (Writer.Chain != Writer.Context->getExternalSource() &&
218           Common->LazySpecializations) {
219         D->LoadLazySpecializations();
220         assert(!Common->LazySpecializations);
221       }
222 
223       ArrayRef<DeclID> LazySpecializations;
224       if (auto *LS = Common->LazySpecializations)
225         LazySpecializations = llvm::ArrayRef(LS + 1, LS[0]);
226 
227       // Add a slot to the record for the number of specializations.
228       unsigned I = Record.size();
229       Record.push_back(0);
230 
231       // AddFirstDeclFromEachModule might trigger deserialization, invalidating
232       // *Specializations iterators.
233       llvm::SmallVector<const Decl*, 16> Specs;
234       for (auto &Entry : Common->Specializations)
235         Specs.push_back(getSpecializationDecl(Entry));
236       for (auto &Entry : getPartialSpecializations(Common))
237         Specs.push_back(getSpecializationDecl(Entry));
238 
239       for (auto *D : Specs) {
240         assert(D->isCanonicalDecl() && "non-canonical decl in set");
241         AddFirstDeclFromEachModule(D, /*IncludeLocal*/true);
242       }
243       Record.append(LazySpecializations.begin(), LazySpecializations.end());
244 
245       // Update the size entry we added earlier.
246       Record[I] = Record.size() - I - 1;
247     }
248 
249     /// Ensure that this template specialization is associated with the specified
250     /// template on reload.
251     void RegisterTemplateSpecialization(const Decl *Template,
252                                         const Decl *Specialization) {
253       Template = Template->getCanonicalDecl();
254 
255       // If the canonical template is local, we'll write out this specialization
256       // when we emit it.
257       // FIXME: We can do the same thing if there is any local declaration of
258       // the template, to avoid emitting an update record.
259       if (!Template->isFromASTFile())
260         return;
261 
262       // We only need to associate the first local declaration of the
263       // specialization. The other declarations will get pulled in by it.
264       if (Writer.getFirstLocalDecl(Specialization) != Specialization)
265         return;
266 
267       Writer.DeclUpdates[Template].push_back(ASTWriter::DeclUpdate(
268           UPD_CXX_ADDED_TEMPLATE_SPECIALIZATION, Specialization));
269     }
270   };
271 }
272 
273 void ASTDeclWriter::Visit(Decl *D) {
274   DeclVisitor<ASTDeclWriter>::Visit(D);
275 
276   // Source locations require array (variable-length) abbreviations.  The
277   // abbreviation infrastructure requires that arrays are encoded last, so
278   // we handle it here in the case of those classes derived from DeclaratorDecl
279   if (auto *DD = dyn_cast<DeclaratorDecl>(D)) {
280     if (auto *TInfo = DD->getTypeSourceInfo())
281       Record.AddTypeLoc(TInfo->getTypeLoc());
282   }
283 
284   // Handle FunctionDecl's body here and write it after all other Stmts/Exprs
285   // have been written. We want it last because we will not read it back when
286   // retrieving it from the AST, we'll just lazily set the offset.
287   if (auto *FD = dyn_cast<FunctionDecl>(D)) {
288     Record.push_back(FD->doesThisDeclarationHaveABody());
289     if (FD->doesThisDeclarationHaveABody())
290       Record.AddFunctionDefinition(FD);
291   }
292 
293   // Similar to FunctionDecls, handle VarDecl's initializer here and write it
294   // after all other Stmts/Exprs. We will not read the initializer until after
295   // we have finished recursive deserialization, because it can recursively
296   // refer back to the variable.
297   if (auto *VD = dyn_cast<VarDecl>(D)) {
298     Record.AddVarDeclInit(VD);
299   }
300 
301   // And similarly for FieldDecls. We already serialized whether there is a
302   // default member initializer.
303   if (auto *FD = dyn_cast<FieldDecl>(D)) {
304     if (FD->hasInClassInitializer()) {
305       if (Expr *Init = FD->getInClassInitializer()) {
306         Record.push_back(1);
307         Record.AddStmt(Init);
308       } else {
309         Record.push_back(0);
310         // Initializer has not been instantiated yet.
311       }
312     }
313   }
314 
315   // If this declaration is also a DeclContext, write blocks for the
316   // declarations that lexically stored inside its context and those
317   // declarations that are visible from its context.
318   if (auto *DC = dyn_cast<DeclContext>(D))
319     VisitDeclContext(DC);
320 }
321 
322 void ASTDeclWriter::VisitDecl(Decl *D) {
323   BitsPacker DeclBits;
324 
325   // The order matters here. It will be better to put the bit with higher
326   // probability to be 0 in the end of the bits.
327   //
328   // Since we're using VBR6 format to store it.
329   // It will be pretty effient if all the higher bits are 0.
330   // For example, if we need to pack 8 bits into a value and the stored value
331   // is 0xf0, the actual stored value will be 0b000111'110000, which takes 12
332   // bits actually. However, if we changed the order to be 0x0f, then we can
333   // store it as 0b001111, which takes 6 bits only now.
334   DeclBits.addBits((uint64_t)D->getModuleOwnershipKind(), /*BitWidth=*/3);
335   DeclBits.addBit(D->isReferenced());
336   DeclBits.addBit(D->isUsed(false));
337   DeclBits.addBits(D->getAccess(), /*BitWidth=*/2);
338   DeclBits.addBit(D->isImplicit());
339   DeclBits.addBit(D->getDeclContext() != D->getLexicalDeclContext());
340   DeclBits.addBit(D->hasAttrs());
341   DeclBits.addBit(D->isTopLevelDeclInObjCContainer());
342   DeclBits.addBit(D->isInvalidDecl());
343   Record.push_back(DeclBits);
344 
345   Record.AddDeclRef(cast_or_null<Decl>(D->getDeclContext()));
346   if (D->getDeclContext() != D->getLexicalDeclContext())
347     Record.AddDeclRef(cast_or_null<Decl>(D->getLexicalDeclContext()));
348 
349   if (D->hasAttrs())
350     Record.AddAttributes(D->getAttrs());
351 
352   Record.push_back(Writer.getSubmoduleID(D->getOwningModule()));
353 
354   // If this declaration injected a name into a context different from its
355   // lexical context, and that context is an imported namespace, we need to
356   // update its visible declarations to include this name.
357   //
358   // This happens when we instantiate a class with a friend declaration or a
359   // function with a local extern declaration, for instance.
360   //
361   // FIXME: Can we handle this in AddedVisibleDecl instead?
362   if (D->isOutOfLine()) {
363     auto *DC = D->getDeclContext();
364     while (auto *NS = dyn_cast<NamespaceDecl>(DC->getRedeclContext())) {
365       if (!NS->isFromASTFile())
366         break;
367       Writer.UpdatedDeclContexts.insert(NS->getPrimaryContext());
368       if (!NS->isInlineNamespace())
369         break;
370       DC = NS->getParent();
371     }
372   }
373 }
374 
375 void ASTDeclWriter::VisitPragmaCommentDecl(PragmaCommentDecl *D) {
376   StringRef Arg = D->getArg();
377   Record.push_back(Arg.size());
378   VisitDecl(D);
379   Record.AddSourceLocation(D->getBeginLoc());
380   Record.push_back(D->getCommentKind());
381   Record.AddString(Arg);
382   Code = serialization::DECL_PRAGMA_COMMENT;
383 }
384 
385 void ASTDeclWriter::VisitPragmaDetectMismatchDecl(
386     PragmaDetectMismatchDecl *D) {
387   StringRef Name = D->getName();
388   StringRef Value = D->getValue();
389   Record.push_back(Name.size() + 1 + Value.size());
390   VisitDecl(D);
391   Record.AddSourceLocation(D->getBeginLoc());
392   Record.AddString(Name);
393   Record.AddString(Value);
394   Code = serialization::DECL_PRAGMA_DETECT_MISMATCH;
395 }
396 
397 void ASTDeclWriter::VisitTranslationUnitDecl(TranslationUnitDecl *D) {
398   llvm_unreachable("Translation units aren't directly serialized");
399 }
400 
401 void ASTDeclWriter::VisitNamedDecl(NamedDecl *D) {
402   VisitDecl(D);
403   Record.AddDeclarationName(D->getDeclName());
404   Record.push_back(needsAnonymousDeclarationNumber(D)
405                        ? Writer.getAnonymousDeclarationNumber(D)
406                        : 0);
407 }
408 
409 void ASTDeclWriter::VisitTypeDecl(TypeDecl *D) {
410   VisitNamedDecl(D);
411   Record.AddSourceLocation(D->getBeginLoc());
412   Record.AddTypeRef(QualType(D->getTypeForDecl(), 0));
413 }
414 
415 void ASTDeclWriter::VisitTypedefNameDecl(TypedefNameDecl *D) {
416   VisitRedeclarable(D);
417   VisitTypeDecl(D);
418   Record.AddTypeSourceInfo(D->getTypeSourceInfo());
419   Record.push_back(D->isModed());
420   if (D->isModed())
421     Record.AddTypeRef(D->getUnderlyingType());
422   Record.AddDeclRef(D->getAnonDeclWithTypedefName(false));
423 }
424 
425 void ASTDeclWriter::VisitTypedefDecl(TypedefDecl *D) {
426   VisitTypedefNameDecl(D);
427   if (D->getDeclContext() == D->getLexicalDeclContext() &&
428       !D->hasAttrs() &&
429       !D->isImplicit() &&
430       D->getFirstDecl() == D->getMostRecentDecl() &&
431       !D->isInvalidDecl() &&
432       !D->isTopLevelDeclInObjCContainer() &&
433       !D->isModulePrivate() &&
434       !needsAnonymousDeclarationNumber(D) &&
435       D->getDeclName().getNameKind() == DeclarationName::Identifier)
436     AbbrevToUse = Writer.getDeclTypedefAbbrev();
437 
438   Code = serialization::DECL_TYPEDEF;
439 }
440 
441 void ASTDeclWriter::VisitTypeAliasDecl(TypeAliasDecl *D) {
442   VisitTypedefNameDecl(D);
443   Record.AddDeclRef(D->getDescribedAliasTemplate());
444   Code = serialization::DECL_TYPEALIAS;
445 }
446 
447 void ASTDeclWriter::VisitTagDecl(TagDecl *D) {
448   static_assert(DeclContext::NumTagDeclBits == 23,
449                 "You need to update the serializer after you change the "
450                 "TagDeclBits");
451 
452   VisitRedeclarable(D);
453   VisitTypeDecl(D);
454   Record.push_back(D->getIdentifierNamespace());
455 
456   BitsPacker TagDeclBits;
457   TagDeclBits.addBits(llvm::to_underlying(D->getTagKind()), /*BitWidth=*/3);
458   TagDeclBits.addBit(!isa<CXXRecordDecl>(D) ? D->isCompleteDefinition() : 0);
459   TagDeclBits.addBit(D->isEmbeddedInDeclarator());
460   TagDeclBits.addBit(D->isFreeStanding());
461   TagDeclBits.addBit(D->isCompleteDefinitionRequired());
462   TagDeclBits.addBits(
463       D->hasExtInfo() ? 1 : (D->getTypedefNameForAnonDecl() ? 2 : 0),
464       /*BitWidth=*/2);
465   Record.push_back(TagDeclBits);
466 
467   Record.AddSourceRange(D->getBraceRange());
468 
469   if (D->hasExtInfo()) {
470     Record.AddQualifierInfo(*D->getExtInfo());
471   } else if (auto *TD = D->getTypedefNameForAnonDecl()) {
472     Record.AddDeclRef(TD);
473     Record.AddIdentifierRef(TD->getDeclName().getAsIdentifierInfo());
474   }
475 }
476 
477 void ASTDeclWriter::VisitEnumDecl(EnumDecl *D) {
478   static_assert(DeclContext::NumEnumDeclBits == 43,
479                 "You need to update the serializer after you change the "
480                 "EnumDeclBits");
481 
482   VisitTagDecl(D);
483   Record.AddTypeSourceInfo(D->getIntegerTypeSourceInfo());
484   if (!D->getIntegerTypeSourceInfo())
485     Record.AddTypeRef(D->getIntegerType());
486   Record.AddTypeRef(D->getPromotionType());
487 
488   BitsPacker EnumDeclBits;
489   EnumDeclBits.addBits(D->getNumPositiveBits(), /*BitWidth=*/8);
490   EnumDeclBits.addBits(D->getNumNegativeBits(), /*BitWidth=*/8);
491   bool ShouldSkipCheckingODR = D->shouldSkipCheckingODR();
492   EnumDeclBits.addBit(ShouldSkipCheckingODR);
493   EnumDeclBits.addBit(D->isScoped());
494   EnumDeclBits.addBit(D->isScopedUsingClassTag());
495   EnumDeclBits.addBit(D->isFixed());
496   Record.push_back(EnumDeclBits);
497 
498   // We only perform ODR checks for decls not in GMF.
499   if (!ShouldSkipCheckingODR)
500     Record.push_back(D->getODRHash());
501 
502   if (MemberSpecializationInfo *MemberInfo = D->getMemberSpecializationInfo()) {
503     Record.AddDeclRef(MemberInfo->getInstantiatedFrom());
504     Record.push_back(MemberInfo->getTemplateSpecializationKind());
505     Record.AddSourceLocation(MemberInfo->getPointOfInstantiation());
506   } else {
507     Record.AddDeclRef(nullptr);
508   }
509 
510   if (D->getDeclContext() == D->getLexicalDeclContext() && !D->hasAttrs() &&
511       !D->isInvalidDecl() && !D->isImplicit() && !D->hasExtInfo() &&
512       !D->getTypedefNameForAnonDecl() &&
513       D->getFirstDecl() == D->getMostRecentDecl() &&
514       !D->isTopLevelDeclInObjCContainer() &&
515       !CXXRecordDecl::classofKind(D->getKind()) &&
516       !D->getIntegerTypeSourceInfo() && !D->getMemberSpecializationInfo() &&
517       !needsAnonymousDeclarationNumber(D) && !D->shouldSkipCheckingODR() &&
518       D->getDeclName().getNameKind() == DeclarationName::Identifier)
519     AbbrevToUse = Writer.getDeclEnumAbbrev();
520 
521   Code = serialization::DECL_ENUM;
522 }
523 
524 void ASTDeclWriter::VisitRecordDecl(RecordDecl *D) {
525   static_assert(DeclContext::NumRecordDeclBits == 64,
526                 "You need to update the serializer after you change the "
527                 "RecordDeclBits");
528 
529   VisitTagDecl(D);
530 
531   BitsPacker RecordDeclBits;
532   RecordDeclBits.addBit(D->hasFlexibleArrayMember());
533   RecordDeclBits.addBit(D->isAnonymousStructOrUnion());
534   RecordDeclBits.addBit(D->hasObjectMember());
535   RecordDeclBits.addBit(D->hasVolatileMember());
536   RecordDeclBits.addBit(D->isNonTrivialToPrimitiveDefaultInitialize());
537   RecordDeclBits.addBit(D->isNonTrivialToPrimitiveCopy());
538   RecordDeclBits.addBit(D->isNonTrivialToPrimitiveDestroy());
539   RecordDeclBits.addBit(D->hasNonTrivialToPrimitiveDefaultInitializeCUnion());
540   RecordDeclBits.addBit(D->hasNonTrivialToPrimitiveDestructCUnion());
541   RecordDeclBits.addBit(D->hasNonTrivialToPrimitiveCopyCUnion());
542   RecordDeclBits.addBit(D->isParamDestroyedInCallee());
543   RecordDeclBits.addBits(llvm::to_underlying(D->getArgPassingRestrictions()), 2);
544   Record.push_back(RecordDeclBits);
545 
546   // Only compute this for C/Objective-C, in C++ this is computed as part
547   // of CXXRecordDecl.
548   if (!isa<CXXRecordDecl>(D))
549     Record.push_back(D->getODRHash());
550 
551   if (D->getDeclContext() == D->getLexicalDeclContext() && !D->hasAttrs() &&
552       !D->isImplicit() && !D->isInvalidDecl() && !D->hasExtInfo() &&
553       !D->getTypedefNameForAnonDecl() &&
554       D->getFirstDecl() == D->getMostRecentDecl() &&
555       !D->isTopLevelDeclInObjCContainer() &&
556       !CXXRecordDecl::classofKind(D->getKind()) &&
557       !needsAnonymousDeclarationNumber(D) &&
558       D->getDeclName().getNameKind() == DeclarationName::Identifier)
559     AbbrevToUse = Writer.getDeclRecordAbbrev();
560 
561   Code = serialization::DECL_RECORD;
562 }
563 
564 void ASTDeclWriter::VisitValueDecl(ValueDecl *D) {
565   VisitNamedDecl(D);
566   Record.AddTypeRef(D->getType());
567 }
568 
569 void ASTDeclWriter::VisitEnumConstantDecl(EnumConstantDecl *D) {
570   VisitValueDecl(D);
571   Record.push_back(D->getInitExpr()? 1 : 0);
572   if (D->getInitExpr())
573     Record.AddStmt(D->getInitExpr());
574   Record.AddAPSInt(D->getInitVal());
575 
576   Code = serialization::DECL_ENUM_CONSTANT;
577 }
578 
579 void ASTDeclWriter::VisitDeclaratorDecl(DeclaratorDecl *D) {
580   VisitValueDecl(D);
581   Record.AddSourceLocation(D->getInnerLocStart());
582   Record.push_back(D->hasExtInfo());
583   if (D->hasExtInfo()) {
584     DeclaratorDecl::ExtInfo *Info = D->getExtInfo();
585     Record.AddQualifierInfo(*Info);
586     Record.AddStmt(Info->TrailingRequiresClause);
587   }
588   // The location information is deferred until the end of the record.
589   Record.AddTypeRef(D->getTypeSourceInfo() ? D->getTypeSourceInfo()->getType()
590                                            : QualType());
591 }
592 
593 void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
594   static_assert(DeclContext::NumFunctionDeclBits == 44,
595                 "You need to update the serializer after you change the "
596                 "FunctionDeclBits");
597 
598   VisitRedeclarable(D);
599 
600   Record.push_back(D->getTemplatedKind());
601   switch (D->getTemplatedKind()) {
602   case FunctionDecl::TK_NonTemplate:
603     break;
604   case FunctionDecl::TK_DependentNonTemplate:
605     Record.AddDeclRef(D->getInstantiatedFromDecl());
606     break;
607   case FunctionDecl::TK_FunctionTemplate:
608     Record.AddDeclRef(D->getDescribedFunctionTemplate());
609     break;
610   case FunctionDecl::TK_MemberSpecialization: {
611     MemberSpecializationInfo *MemberInfo = D->getMemberSpecializationInfo();
612     Record.AddDeclRef(MemberInfo->getInstantiatedFrom());
613     Record.push_back(MemberInfo->getTemplateSpecializationKind());
614     Record.AddSourceLocation(MemberInfo->getPointOfInstantiation());
615     break;
616   }
617   case FunctionDecl::TK_FunctionTemplateSpecialization: {
618     FunctionTemplateSpecializationInfo *
619       FTSInfo = D->getTemplateSpecializationInfo();
620 
621     RegisterTemplateSpecialization(FTSInfo->getTemplate(), D);
622 
623     Record.AddDeclRef(FTSInfo->getTemplate());
624     Record.push_back(FTSInfo->getTemplateSpecializationKind());
625 
626     // Template arguments.
627     Record.AddTemplateArgumentList(FTSInfo->TemplateArguments);
628 
629     // Template args as written.
630     Record.push_back(FTSInfo->TemplateArgumentsAsWritten != nullptr);
631     if (FTSInfo->TemplateArgumentsAsWritten)
632       Record.AddASTTemplateArgumentListInfo(
633           FTSInfo->TemplateArgumentsAsWritten);
634 
635     Record.AddSourceLocation(FTSInfo->getPointOfInstantiation());
636 
637     if (MemberSpecializationInfo *MemberInfo =
638         FTSInfo->getMemberSpecializationInfo()) {
639       Record.push_back(1);
640       Record.AddDeclRef(MemberInfo->getInstantiatedFrom());
641       Record.push_back(MemberInfo->getTemplateSpecializationKind());
642       Record.AddSourceLocation(MemberInfo->getPointOfInstantiation());
643     } else {
644       Record.push_back(0);
645     }
646 
647     if (D->isCanonicalDecl()) {
648       // Write the template that contains the specializations set. We will
649       // add a FunctionTemplateSpecializationInfo to it when reading.
650       Record.AddDeclRef(FTSInfo->getTemplate()->getCanonicalDecl());
651     }
652     break;
653   }
654   case FunctionDecl::TK_DependentFunctionTemplateSpecialization: {
655     DependentFunctionTemplateSpecializationInfo *
656       DFTSInfo = D->getDependentSpecializationInfo();
657 
658     // Candidates.
659     Record.push_back(DFTSInfo->getCandidates().size());
660     for (FunctionTemplateDecl *FTD : DFTSInfo->getCandidates())
661       Record.AddDeclRef(FTD);
662 
663     // Templates args.
664     Record.push_back(DFTSInfo->TemplateArgumentsAsWritten != nullptr);
665     if (DFTSInfo->TemplateArgumentsAsWritten)
666       Record.AddASTTemplateArgumentListInfo(
667           DFTSInfo->TemplateArgumentsAsWritten);
668     break;
669   }
670   }
671 
672   VisitDeclaratorDecl(D);
673   Record.AddDeclarationNameLoc(D->DNLoc, D->getDeclName());
674   Record.push_back(D->getIdentifierNamespace());
675 
676   // The order matters here. It will be better to put the bit with higher
677   // probability to be 0 in the end of the bits. See the comments in VisitDecl
678   // for details.
679   BitsPacker FunctionDeclBits;
680   // FIXME: stable encoding
681   FunctionDeclBits.addBits(llvm::to_underlying(D->getLinkageInternal()), 3);
682   FunctionDeclBits.addBits((uint32_t)D->getStorageClass(), /*BitWidth=*/3);
683   bool ShouldSkipCheckingODR = D->shouldSkipCheckingODR();
684   FunctionDeclBits.addBit(ShouldSkipCheckingODR);
685   FunctionDeclBits.addBit(D->isInlineSpecified());
686   FunctionDeclBits.addBit(D->isInlined());
687   FunctionDeclBits.addBit(D->hasSkippedBody());
688   FunctionDeclBits.addBit(D->isVirtualAsWritten());
689   FunctionDeclBits.addBit(D->isPureVirtual());
690   FunctionDeclBits.addBit(D->hasInheritedPrototype());
691   FunctionDeclBits.addBit(D->hasWrittenPrototype());
692   FunctionDeclBits.addBit(D->isDeletedBit());
693   FunctionDeclBits.addBit(D->isTrivial());
694   FunctionDeclBits.addBit(D->isTrivialForCall());
695   FunctionDeclBits.addBit(D->isDefaulted());
696   FunctionDeclBits.addBit(D->isExplicitlyDefaulted());
697   FunctionDeclBits.addBit(D->isIneligibleOrNotSelected());
698   FunctionDeclBits.addBits((uint64_t)(D->getConstexprKind()), /*BitWidth=*/2);
699   FunctionDeclBits.addBit(D->hasImplicitReturnZero());
700   FunctionDeclBits.addBit(D->isMultiVersion());
701   FunctionDeclBits.addBit(D->isLateTemplateParsed());
702   FunctionDeclBits.addBit(D->FriendConstraintRefersToEnclosingTemplate());
703   FunctionDeclBits.addBit(D->usesSEHTry());
704   Record.push_back(FunctionDeclBits);
705 
706   Record.AddSourceLocation(D->getEndLoc());
707   if (D->isExplicitlyDefaulted())
708     Record.AddSourceLocation(D->getDefaultLoc());
709 
710   // We only perform ODR checks for decls not in GMF.
711   if (!ShouldSkipCheckingODR)
712     Record.push_back(D->getODRHash());
713 
714   if (D->isDefaulted()) {
715     if (auto *FDI = D->getDefaultedFunctionInfo()) {
716       Record.push_back(FDI->getUnqualifiedLookups().size());
717       for (DeclAccessPair P : FDI->getUnqualifiedLookups()) {
718         Record.AddDeclRef(P.getDecl());
719         Record.push_back(P.getAccess());
720       }
721     } else {
722       Record.push_back(0);
723     }
724   }
725 
726   Record.push_back(D->param_size());
727   for (auto *P : D->parameters())
728     Record.AddDeclRef(P);
729   Code = serialization::DECL_FUNCTION;
730 }
731 
732 static void addExplicitSpecifier(ExplicitSpecifier ES,
733                                  ASTRecordWriter &Record) {
734   uint64_t Kind = static_cast<uint64_t>(ES.getKind());
735   Kind = Kind << 1 | static_cast<bool>(ES.getExpr());
736   Record.push_back(Kind);
737   if (ES.getExpr()) {
738     Record.AddStmt(ES.getExpr());
739   }
740 }
741 
742 void ASTDeclWriter::VisitCXXDeductionGuideDecl(CXXDeductionGuideDecl *D) {
743   addExplicitSpecifier(D->getExplicitSpecifier(), Record);
744   Record.AddDeclRef(D->Ctor);
745   VisitFunctionDecl(D);
746   Record.push_back(static_cast<unsigned char>(D->getDeductionCandidateKind()));
747   Code = serialization::DECL_CXX_DEDUCTION_GUIDE;
748 }
749 
750 void ASTDeclWriter::VisitObjCMethodDecl(ObjCMethodDecl *D) {
751   static_assert(DeclContext::NumObjCMethodDeclBits == 37,
752                 "You need to update the serializer after you change the "
753                 "ObjCMethodDeclBits");
754 
755   VisitNamedDecl(D);
756   // FIXME: convert to LazyStmtPtr?
757   // Unlike C/C++, method bodies will never be in header files.
758   bool HasBodyStuff = D->getBody() != nullptr;
759   Record.push_back(HasBodyStuff);
760   if (HasBodyStuff) {
761     Record.AddStmt(D->getBody());
762   }
763   Record.AddDeclRef(D->getSelfDecl());
764   Record.AddDeclRef(D->getCmdDecl());
765   Record.push_back(D->isInstanceMethod());
766   Record.push_back(D->isVariadic());
767   Record.push_back(D->isPropertyAccessor());
768   Record.push_back(D->isSynthesizedAccessorStub());
769   Record.push_back(D->isDefined());
770   Record.push_back(D->isOverriding());
771   Record.push_back(D->hasSkippedBody());
772 
773   Record.push_back(D->isRedeclaration());
774   Record.push_back(D->hasRedeclaration());
775   if (D->hasRedeclaration()) {
776     assert(Context.getObjCMethodRedeclaration(D));
777     Record.AddDeclRef(Context.getObjCMethodRedeclaration(D));
778   }
779 
780   // FIXME: stable encoding for @required/@optional
781   Record.push_back(llvm::to_underlying(D->getImplementationControl()));
782   // FIXME: stable encoding for in/out/inout/bycopy/byref/oneway/nullability
783   Record.push_back(D->getObjCDeclQualifier());
784   Record.push_back(D->hasRelatedResultType());
785   Record.AddTypeRef(D->getReturnType());
786   Record.AddTypeSourceInfo(D->getReturnTypeSourceInfo());
787   Record.AddSourceLocation(D->getEndLoc());
788   Record.push_back(D->param_size());
789   for (const auto *P : D->parameters())
790     Record.AddDeclRef(P);
791 
792   Record.push_back(D->getSelLocsKind());
793   unsigned NumStoredSelLocs = D->getNumStoredSelLocs();
794   SourceLocation *SelLocs = D->getStoredSelLocs();
795   Record.push_back(NumStoredSelLocs);
796   for (unsigned i = 0; i != NumStoredSelLocs; ++i)
797     Record.AddSourceLocation(SelLocs[i]);
798 
799   Code = serialization::DECL_OBJC_METHOD;
800 }
801 
802 void ASTDeclWriter::VisitObjCTypeParamDecl(ObjCTypeParamDecl *D) {
803   VisitTypedefNameDecl(D);
804   Record.push_back(D->Variance);
805   Record.push_back(D->Index);
806   Record.AddSourceLocation(D->VarianceLoc);
807   Record.AddSourceLocation(D->ColonLoc);
808 
809   Code = serialization::DECL_OBJC_TYPE_PARAM;
810 }
811 
812 void ASTDeclWriter::VisitObjCContainerDecl(ObjCContainerDecl *D) {
813   static_assert(DeclContext::NumObjCContainerDeclBits == 64,
814                 "You need to update the serializer after you change the "
815                 "ObjCContainerDeclBits");
816 
817   VisitNamedDecl(D);
818   Record.AddSourceLocation(D->getAtStartLoc());
819   Record.AddSourceRange(D->getAtEndRange());
820   // Abstract class (no need to define a stable serialization::DECL code).
821 }
822 
823 void ASTDeclWriter::VisitObjCInterfaceDecl(ObjCInterfaceDecl *D) {
824   VisitRedeclarable(D);
825   VisitObjCContainerDecl(D);
826   Record.AddTypeRef(QualType(D->getTypeForDecl(), 0));
827   AddObjCTypeParamList(D->TypeParamList);
828 
829   Record.push_back(D->isThisDeclarationADefinition());
830   if (D->isThisDeclarationADefinition()) {
831     // Write the DefinitionData
832     ObjCInterfaceDecl::DefinitionData &Data = D->data();
833 
834     Record.AddTypeSourceInfo(D->getSuperClassTInfo());
835     Record.AddSourceLocation(D->getEndOfDefinitionLoc());
836     Record.push_back(Data.HasDesignatedInitializers);
837     Record.push_back(D->getODRHash());
838 
839     // Write out the protocols that are directly referenced by the @interface.
840     Record.push_back(Data.ReferencedProtocols.size());
841     for (const auto *P : D->protocols())
842       Record.AddDeclRef(P);
843     for (const auto &PL : D->protocol_locs())
844       Record.AddSourceLocation(PL);
845 
846     // Write out the protocols that are transitively referenced.
847     Record.push_back(Data.AllReferencedProtocols.size());
848     for (ObjCList<ObjCProtocolDecl>::iterator
849               P = Data.AllReferencedProtocols.begin(),
850            PEnd = Data.AllReferencedProtocols.end();
851          P != PEnd; ++P)
852       Record.AddDeclRef(*P);
853 
854 
855     if (ObjCCategoryDecl *Cat = D->getCategoryListRaw()) {
856       // Ensure that we write out the set of categories for this class.
857       Writer.ObjCClassesWithCategories.insert(D);
858 
859       // Make sure that the categories get serialized.
860       for (; Cat; Cat = Cat->getNextClassCategoryRaw())
861         (void)Writer.GetDeclRef(Cat);
862     }
863   }
864 
865   Code = serialization::DECL_OBJC_INTERFACE;
866 }
867 
868 void ASTDeclWriter::VisitObjCIvarDecl(ObjCIvarDecl *D) {
869   VisitFieldDecl(D);
870   // FIXME: stable encoding for @public/@private/@protected/@package
871   Record.push_back(D->getAccessControl());
872   Record.push_back(D->getSynthesize());
873 
874   if (D->getDeclContext() == D->getLexicalDeclContext() &&
875       !D->hasAttrs() &&
876       !D->isImplicit() &&
877       !D->isUsed(false) &&
878       !D->isInvalidDecl() &&
879       !D->isReferenced() &&
880       !D->isModulePrivate() &&
881       !D->getBitWidth() &&
882       !D->hasExtInfo() &&
883       D->getDeclName())
884     AbbrevToUse = Writer.getDeclObjCIvarAbbrev();
885 
886   Code = serialization::DECL_OBJC_IVAR;
887 }
888 
889 void ASTDeclWriter::VisitObjCProtocolDecl(ObjCProtocolDecl *D) {
890   VisitRedeclarable(D);
891   VisitObjCContainerDecl(D);
892 
893   Record.push_back(D->isThisDeclarationADefinition());
894   if (D->isThisDeclarationADefinition()) {
895     Record.push_back(D->protocol_size());
896     for (const auto *I : D->protocols())
897       Record.AddDeclRef(I);
898     for (const auto &PL : D->protocol_locs())
899       Record.AddSourceLocation(PL);
900     Record.push_back(D->getODRHash());
901   }
902 
903   Code = serialization::DECL_OBJC_PROTOCOL;
904 }
905 
906 void ASTDeclWriter::VisitObjCAtDefsFieldDecl(ObjCAtDefsFieldDecl *D) {
907   VisitFieldDecl(D);
908   Code = serialization::DECL_OBJC_AT_DEFS_FIELD;
909 }
910 
911 void ASTDeclWriter::VisitObjCCategoryDecl(ObjCCategoryDecl *D) {
912   VisitObjCContainerDecl(D);
913   Record.AddSourceLocation(D->getCategoryNameLoc());
914   Record.AddSourceLocation(D->getIvarLBraceLoc());
915   Record.AddSourceLocation(D->getIvarRBraceLoc());
916   Record.AddDeclRef(D->getClassInterface());
917   AddObjCTypeParamList(D->TypeParamList);
918   Record.push_back(D->protocol_size());
919   for (const auto *I : D->protocols())
920     Record.AddDeclRef(I);
921   for (const auto &PL : D->protocol_locs())
922     Record.AddSourceLocation(PL);
923   Code = serialization::DECL_OBJC_CATEGORY;
924 }
925 
926 void ASTDeclWriter::VisitObjCCompatibleAliasDecl(ObjCCompatibleAliasDecl *D) {
927   VisitNamedDecl(D);
928   Record.AddDeclRef(D->getClassInterface());
929   Code = serialization::DECL_OBJC_COMPATIBLE_ALIAS;
930 }
931 
932 void ASTDeclWriter::VisitObjCPropertyDecl(ObjCPropertyDecl *D) {
933   VisitNamedDecl(D);
934   Record.AddSourceLocation(D->getAtLoc());
935   Record.AddSourceLocation(D->getLParenLoc());
936   Record.AddTypeRef(D->getType());
937   Record.AddTypeSourceInfo(D->getTypeSourceInfo());
938   // FIXME: stable encoding
939   Record.push_back((unsigned)D->getPropertyAttributes());
940   Record.push_back((unsigned)D->getPropertyAttributesAsWritten());
941   // FIXME: stable encoding
942   Record.push_back((unsigned)D->getPropertyImplementation());
943   Record.AddDeclarationName(D->getGetterName());
944   Record.AddSourceLocation(D->getGetterNameLoc());
945   Record.AddDeclarationName(D->getSetterName());
946   Record.AddSourceLocation(D->getSetterNameLoc());
947   Record.AddDeclRef(D->getGetterMethodDecl());
948   Record.AddDeclRef(D->getSetterMethodDecl());
949   Record.AddDeclRef(D->getPropertyIvarDecl());
950   Code = serialization::DECL_OBJC_PROPERTY;
951 }
952 
953 void ASTDeclWriter::VisitObjCImplDecl(ObjCImplDecl *D) {
954   VisitObjCContainerDecl(D);
955   Record.AddDeclRef(D->getClassInterface());
956   // Abstract class (no need to define a stable serialization::DECL code).
957 }
958 
959 void ASTDeclWriter::VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D) {
960   VisitObjCImplDecl(D);
961   Record.AddSourceLocation(D->getCategoryNameLoc());
962   Code = serialization::DECL_OBJC_CATEGORY_IMPL;
963 }
964 
965 void ASTDeclWriter::VisitObjCImplementationDecl(ObjCImplementationDecl *D) {
966   VisitObjCImplDecl(D);
967   Record.AddDeclRef(D->getSuperClass());
968   Record.AddSourceLocation(D->getSuperClassLoc());
969   Record.AddSourceLocation(D->getIvarLBraceLoc());
970   Record.AddSourceLocation(D->getIvarRBraceLoc());
971   Record.push_back(D->hasNonZeroConstructors());
972   Record.push_back(D->hasDestructors());
973   Record.push_back(D->NumIvarInitializers);
974   if (D->NumIvarInitializers)
975     Record.AddCXXCtorInitializers(
976         llvm::ArrayRef(D->init_begin(), D->init_end()));
977   Code = serialization::DECL_OBJC_IMPLEMENTATION;
978 }
979 
980 void ASTDeclWriter::VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D) {
981   VisitDecl(D);
982   Record.AddSourceLocation(D->getBeginLoc());
983   Record.AddDeclRef(D->getPropertyDecl());
984   Record.AddDeclRef(D->getPropertyIvarDecl());
985   Record.AddSourceLocation(D->getPropertyIvarDeclLoc());
986   Record.AddDeclRef(D->getGetterMethodDecl());
987   Record.AddDeclRef(D->getSetterMethodDecl());
988   Record.AddStmt(D->getGetterCXXConstructor());
989   Record.AddStmt(D->getSetterCXXAssignment());
990   Code = serialization::DECL_OBJC_PROPERTY_IMPL;
991 }
992 
993 void ASTDeclWriter::VisitFieldDecl(FieldDecl *D) {
994   VisitDeclaratorDecl(D);
995   Record.push_back(D->isMutable());
996 
997   Record.push_back((D->StorageKind << 1) | D->BitField);
998   if (D->StorageKind == FieldDecl::ISK_CapturedVLAType)
999     Record.AddTypeRef(QualType(D->getCapturedVLAType(), 0));
1000   else if (D->BitField)
1001     Record.AddStmt(D->getBitWidth());
1002 
1003   if (!D->getDeclName())
1004     Record.AddDeclRef(Context.getInstantiatedFromUnnamedFieldDecl(D));
1005 
1006   if (D->getDeclContext() == D->getLexicalDeclContext() &&
1007       !D->hasAttrs() &&
1008       !D->isImplicit() &&
1009       !D->isUsed(false) &&
1010       !D->isInvalidDecl() &&
1011       !D->isReferenced() &&
1012       !D->isTopLevelDeclInObjCContainer() &&
1013       !D->isModulePrivate() &&
1014       !D->getBitWidth() &&
1015       !D->hasInClassInitializer() &&
1016       !D->hasCapturedVLAType() &&
1017       !D->hasExtInfo() &&
1018       !ObjCIvarDecl::classofKind(D->getKind()) &&
1019       !ObjCAtDefsFieldDecl::classofKind(D->getKind()) &&
1020       D->getDeclName())
1021     AbbrevToUse = Writer.getDeclFieldAbbrev();
1022 
1023   Code = serialization::DECL_FIELD;
1024 }
1025 
1026 void ASTDeclWriter::VisitMSPropertyDecl(MSPropertyDecl *D) {
1027   VisitDeclaratorDecl(D);
1028   Record.AddIdentifierRef(D->getGetterId());
1029   Record.AddIdentifierRef(D->getSetterId());
1030   Code = serialization::DECL_MS_PROPERTY;
1031 }
1032 
1033 void ASTDeclWriter::VisitMSGuidDecl(MSGuidDecl *D) {
1034   VisitValueDecl(D);
1035   MSGuidDecl::Parts Parts = D->getParts();
1036   Record.push_back(Parts.Part1);
1037   Record.push_back(Parts.Part2);
1038   Record.push_back(Parts.Part3);
1039   Record.append(std::begin(Parts.Part4And5), std::end(Parts.Part4And5));
1040   Code = serialization::DECL_MS_GUID;
1041 }
1042 
1043 void ASTDeclWriter::VisitUnnamedGlobalConstantDecl(
1044     UnnamedGlobalConstantDecl *D) {
1045   VisitValueDecl(D);
1046   Record.AddAPValue(D->getValue());
1047   Code = serialization::DECL_UNNAMED_GLOBAL_CONSTANT;
1048 }
1049 
1050 void ASTDeclWriter::VisitTemplateParamObjectDecl(TemplateParamObjectDecl *D) {
1051   VisitValueDecl(D);
1052   Record.AddAPValue(D->getValue());
1053   Code = serialization::DECL_TEMPLATE_PARAM_OBJECT;
1054 }
1055 
1056 void ASTDeclWriter::VisitIndirectFieldDecl(IndirectFieldDecl *D) {
1057   VisitValueDecl(D);
1058   Record.push_back(D->getChainingSize());
1059 
1060   for (const auto *P : D->chain())
1061     Record.AddDeclRef(P);
1062   Code = serialization::DECL_INDIRECTFIELD;
1063 }
1064 
1065 void ASTDeclWriter::VisitVarDecl(VarDecl *D) {
1066   VisitRedeclarable(D);
1067   VisitDeclaratorDecl(D);
1068 
1069   // The order matters here. It will be better to put the bit with higher
1070   // probability to be 0 in the end of the bits. See the comments in VisitDecl
1071   // for details.
1072   BitsPacker VarDeclBits;
1073   VarDeclBits.addBits(llvm::to_underlying(D->getLinkageInternal()),
1074                       /*BitWidth=*/3);
1075 
1076   bool ModulesCodegen = false;
1077   if (Writer.WritingModule && D->getStorageDuration() == SD_Static &&
1078       !D->getDescribedVarTemplate()) {
1079     // When building a C++20 module interface unit or a partition unit, a
1080     // strong definition in the module interface is provided by the
1081     // compilation of that unit, not by its users. (Inline variables are still
1082     // emitted in module users.)
1083     ModulesCodegen =
1084         (Writer.WritingModule->isInterfaceOrPartition() ||
1085          (D->hasAttr<DLLExportAttr>() &&
1086           Writer.Context->getLangOpts().BuildingPCHWithObjectFile)) &&
1087         Writer.Context->GetGVALinkageForVariable(D) >= GVA_StrongExternal;
1088   }
1089   VarDeclBits.addBit(ModulesCodegen);
1090 
1091   VarDeclBits.addBits(D->getStorageClass(), /*BitWidth=*/3);
1092   VarDeclBits.addBits(D->getTSCSpec(), /*BitWidth=*/2);
1093   VarDeclBits.addBits(D->getInitStyle(), /*BitWidth=*/2);
1094   VarDeclBits.addBit(D->isARCPseudoStrong());
1095 
1096   bool HasDeducedType = false;
1097   if (!isa<ParmVarDecl>(D)) {
1098     VarDeclBits.addBit(D->isThisDeclarationADemotedDefinition());
1099     VarDeclBits.addBit(D->isExceptionVariable());
1100     VarDeclBits.addBit(D->isNRVOVariable());
1101     VarDeclBits.addBit(D->isCXXForRangeDecl());
1102 
1103     VarDeclBits.addBit(D->isInline());
1104     VarDeclBits.addBit(D->isInlineSpecified());
1105     VarDeclBits.addBit(D->isConstexpr());
1106     VarDeclBits.addBit(D->isInitCapture());
1107     VarDeclBits.addBit(D->isPreviousDeclInSameBlockScope());
1108 
1109     VarDeclBits.addBit(D->isEscapingByref());
1110     HasDeducedType = D->getType()->getContainedDeducedType();
1111     VarDeclBits.addBit(HasDeducedType);
1112 
1113     if (const auto *IPD = dyn_cast<ImplicitParamDecl>(D))
1114       VarDeclBits.addBits(llvm::to_underlying(IPD->getParameterKind()),
1115                           /*Width=*/3);
1116     else
1117       VarDeclBits.addBits(0, /*Width=*/3);
1118 
1119     VarDeclBits.addBit(D->isObjCForDecl());
1120   }
1121 
1122   Record.push_back(VarDeclBits);
1123 
1124   if (ModulesCodegen)
1125     Writer.ModularCodegenDecls.push_back(Writer.GetDeclRef(D));
1126 
1127   if (D->hasAttr<BlocksAttr>()) {
1128     BlockVarCopyInit Init = Writer.Context->getBlockVarCopyInit(D);
1129     Record.AddStmt(Init.getCopyExpr());
1130     if (Init.getCopyExpr())
1131       Record.push_back(Init.canThrow());
1132   }
1133 
1134   enum {
1135     VarNotTemplate = 0, VarTemplate, StaticDataMemberSpecialization
1136   };
1137   if (VarTemplateDecl *TemplD = D->getDescribedVarTemplate()) {
1138     Record.push_back(VarTemplate);
1139     Record.AddDeclRef(TemplD);
1140   } else if (MemberSpecializationInfo *SpecInfo
1141                = D->getMemberSpecializationInfo()) {
1142     Record.push_back(StaticDataMemberSpecialization);
1143     Record.AddDeclRef(SpecInfo->getInstantiatedFrom());
1144     Record.push_back(SpecInfo->getTemplateSpecializationKind());
1145     Record.AddSourceLocation(SpecInfo->getPointOfInstantiation());
1146   } else {
1147     Record.push_back(VarNotTemplate);
1148   }
1149 
1150   if (D->getDeclContext() == D->getLexicalDeclContext() && !D->hasAttrs() &&
1151       !D->isTopLevelDeclInObjCContainer() &&
1152       !needsAnonymousDeclarationNumber(D) &&
1153       D->getDeclName().getNameKind() == DeclarationName::Identifier &&
1154       !D->hasExtInfo() && D->getFirstDecl() == D->getMostRecentDecl() &&
1155       D->getKind() == Decl::Var && !D->isInline() && !D->isConstexpr() &&
1156       !D->isInitCapture() && !D->isPreviousDeclInSameBlockScope() &&
1157       !D->isEscapingByref() && !HasDeducedType &&
1158       D->getStorageDuration() != SD_Static && !D->getDescribedVarTemplate() &&
1159       !D->getMemberSpecializationInfo() && !D->isObjCForDecl() &&
1160       !isa<ImplicitParamDecl>(D) && !D->isEscapingByref())
1161     AbbrevToUse = Writer.getDeclVarAbbrev();
1162 
1163   Code = serialization::DECL_VAR;
1164 }
1165 
1166 void ASTDeclWriter::VisitImplicitParamDecl(ImplicitParamDecl *D) {
1167   VisitVarDecl(D);
1168   Code = serialization::DECL_IMPLICIT_PARAM;
1169 }
1170 
1171 void ASTDeclWriter::VisitParmVarDecl(ParmVarDecl *D) {
1172   VisitVarDecl(D);
1173 
1174   // See the implementation of `ParmVarDecl::getParameterIndex()`, which may
1175   // exceed the size of the normal bitfield. So it may be better to not pack
1176   // these bits.
1177   Record.push_back(D->getFunctionScopeIndex());
1178 
1179   BitsPacker ParmVarDeclBits;
1180   ParmVarDeclBits.addBit(D->isObjCMethodParameter());
1181   ParmVarDeclBits.addBits(D->getFunctionScopeDepth(), /*BitsWidth=*/7);
1182   // FIXME: stable encoding
1183   ParmVarDeclBits.addBits(D->getObjCDeclQualifier(), /*BitsWidth=*/7);
1184   ParmVarDeclBits.addBit(D->isKNRPromoted());
1185   ParmVarDeclBits.addBit(D->hasInheritedDefaultArg());
1186   ParmVarDeclBits.addBit(D->hasUninstantiatedDefaultArg());
1187   ParmVarDeclBits.addBit(D->getExplicitObjectParamThisLoc().isValid());
1188   Record.push_back(ParmVarDeclBits);
1189 
1190   if (D->hasUninstantiatedDefaultArg())
1191     Record.AddStmt(D->getUninstantiatedDefaultArg());
1192   if (D->getExplicitObjectParamThisLoc().isValid())
1193     Record.AddSourceLocation(D->getExplicitObjectParamThisLoc());
1194   Code = serialization::DECL_PARM_VAR;
1195 
1196   // If the assumptions about the DECL_PARM_VAR abbrev are true, use it.  Here
1197   // we dynamically check for the properties that we optimize for, but don't
1198   // know are true of all PARM_VAR_DECLs.
1199   if (D->getDeclContext() == D->getLexicalDeclContext() && !D->hasAttrs() &&
1200       !D->hasExtInfo() && D->getStorageClass() == 0 && !D->isInvalidDecl() &&
1201       !D->isTopLevelDeclInObjCContainer() &&
1202       D->getInitStyle() == VarDecl::CInit && // Can params have anything else?
1203       D->getInit() == nullptr)               // No default expr.
1204     AbbrevToUse = Writer.getDeclParmVarAbbrev();
1205 
1206   // Check things we know are true of *every* PARM_VAR_DECL, which is more than
1207   // just us assuming it.
1208   assert(!D->getTSCSpec() && "PARM_VAR_DECL can't use TLS");
1209   assert(!D->isThisDeclarationADemotedDefinition()
1210          && "PARM_VAR_DECL can't be demoted definition.");
1211   assert(D->getAccess() == AS_none && "PARM_VAR_DECL can't be public/private");
1212   assert(!D->isExceptionVariable() && "PARM_VAR_DECL can't be exception var");
1213   assert(D->getPreviousDecl() == nullptr && "PARM_VAR_DECL can't be redecl");
1214   assert(!D->isStaticDataMember() &&
1215          "PARM_VAR_DECL can't be static data member");
1216 }
1217 
1218 void ASTDeclWriter::VisitDecompositionDecl(DecompositionDecl *D) {
1219   // Record the number of bindings first to simplify deserialization.
1220   Record.push_back(D->bindings().size());
1221 
1222   VisitVarDecl(D);
1223   for (auto *B : D->bindings())
1224     Record.AddDeclRef(B);
1225   Code = serialization::DECL_DECOMPOSITION;
1226 }
1227 
1228 void ASTDeclWriter::VisitBindingDecl(BindingDecl *D) {
1229   VisitValueDecl(D);
1230   Record.AddStmt(D->getBinding());
1231   Code = serialization::DECL_BINDING;
1232 }
1233 
1234 void ASTDeclWriter::VisitFileScopeAsmDecl(FileScopeAsmDecl *D) {
1235   VisitDecl(D);
1236   Record.AddStmt(D->getAsmString());
1237   Record.AddSourceLocation(D->getRParenLoc());
1238   Code = serialization::DECL_FILE_SCOPE_ASM;
1239 }
1240 
1241 void ASTDeclWriter::VisitTopLevelStmtDecl(TopLevelStmtDecl *D) {
1242   VisitDecl(D);
1243   Record.AddStmt(D->getStmt());
1244   Code = serialization::DECL_TOP_LEVEL_STMT_DECL;
1245 }
1246 
1247 void ASTDeclWriter::VisitEmptyDecl(EmptyDecl *D) {
1248   VisitDecl(D);
1249   Code = serialization::DECL_EMPTY;
1250 }
1251 
1252 void ASTDeclWriter::VisitLifetimeExtendedTemporaryDecl(
1253     LifetimeExtendedTemporaryDecl *D) {
1254   VisitDecl(D);
1255   Record.AddDeclRef(D->getExtendingDecl());
1256   Record.AddStmt(D->getTemporaryExpr());
1257   Record.push_back(static_cast<bool>(D->getValue()));
1258   if (D->getValue())
1259     Record.AddAPValue(*D->getValue());
1260   Record.push_back(D->getManglingNumber());
1261   Code = serialization::DECL_LIFETIME_EXTENDED_TEMPORARY;
1262 }
1263 void ASTDeclWriter::VisitBlockDecl(BlockDecl *D) {
1264   VisitDecl(D);
1265   Record.AddStmt(D->getBody());
1266   Record.AddTypeSourceInfo(D->getSignatureAsWritten());
1267   Record.push_back(D->param_size());
1268   for (ParmVarDecl *P : D->parameters())
1269     Record.AddDeclRef(P);
1270   Record.push_back(D->isVariadic());
1271   Record.push_back(D->blockMissingReturnType());
1272   Record.push_back(D->isConversionFromLambda());
1273   Record.push_back(D->doesNotEscape());
1274   Record.push_back(D->canAvoidCopyToHeap());
1275   Record.push_back(D->capturesCXXThis());
1276   Record.push_back(D->getNumCaptures());
1277   for (const auto &capture : D->captures()) {
1278     Record.AddDeclRef(capture.getVariable());
1279 
1280     unsigned flags = 0;
1281     if (capture.isByRef()) flags |= 1;
1282     if (capture.isNested()) flags |= 2;
1283     if (capture.hasCopyExpr()) flags |= 4;
1284     Record.push_back(flags);
1285 
1286     if (capture.hasCopyExpr()) Record.AddStmt(capture.getCopyExpr());
1287   }
1288 
1289   Code = serialization::DECL_BLOCK;
1290 }
1291 
1292 void ASTDeclWriter::VisitCapturedDecl(CapturedDecl *CD) {
1293   Record.push_back(CD->getNumParams());
1294   VisitDecl(CD);
1295   Record.push_back(CD->getContextParamPosition());
1296   Record.push_back(CD->isNothrow() ? 1 : 0);
1297   // Body is stored by VisitCapturedStmt.
1298   for (unsigned I = 0; I < CD->getNumParams(); ++I)
1299     Record.AddDeclRef(CD->getParam(I));
1300   Code = serialization::DECL_CAPTURED;
1301 }
1302 
1303 void ASTDeclWriter::VisitLinkageSpecDecl(LinkageSpecDecl *D) {
1304   static_assert(DeclContext::NumLinkageSpecDeclBits == 17,
1305                 "You need to update the serializer after you change the"
1306                 "LinkageSpecDeclBits");
1307 
1308   VisitDecl(D);
1309   Record.push_back(llvm::to_underlying(D->getLanguage()));
1310   Record.AddSourceLocation(D->getExternLoc());
1311   Record.AddSourceLocation(D->getRBraceLoc());
1312   Code = serialization::DECL_LINKAGE_SPEC;
1313 }
1314 
1315 void ASTDeclWriter::VisitExportDecl(ExportDecl *D) {
1316   VisitDecl(D);
1317   Record.AddSourceLocation(D->getRBraceLoc());
1318   Code = serialization::DECL_EXPORT;
1319 }
1320 
1321 void ASTDeclWriter::VisitLabelDecl(LabelDecl *D) {
1322   VisitNamedDecl(D);
1323   Record.AddSourceLocation(D->getBeginLoc());
1324   Code = serialization::DECL_LABEL;
1325 }
1326 
1327 
1328 void ASTDeclWriter::VisitNamespaceDecl(NamespaceDecl *D) {
1329   VisitRedeclarable(D);
1330   VisitNamedDecl(D);
1331 
1332   BitsPacker NamespaceDeclBits;
1333   NamespaceDeclBits.addBit(D->isInline());
1334   NamespaceDeclBits.addBit(D->isNested());
1335   Record.push_back(NamespaceDeclBits);
1336 
1337   Record.AddSourceLocation(D->getBeginLoc());
1338   Record.AddSourceLocation(D->getRBraceLoc());
1339 
1340   if (D->isOriginalNamespace())
1341     Record.AddDeclRef(D->getAnonymousNamespace());
1342   Code = serialization::DECL_NAMESPACE;
1343 
1344   if (Writer.hasChain() && D->isAnonymousNamespace() &&
1345       D == D->getMostRecentDecl()) {
1346     // This is a most recent reopening of the anonymous namespace. If its parent
1347     // is in a previous PCH (or is the TU), mark that parent for update, because
1348     // the original namespace always points to the latest re-opening of its
1349     // anonymous namespace.
1350     Decl *Parent = cast<Decl>(
1351         D->getParent()->getRedeclContext()->getPrimaryContext());
1352     if (Parent->isFromASTFile() || isa<TranslationUnitDecl>(Parent)) {
1353       Writer.DeclUpdates[Parent].push_back(
1354           ASTWriter::DeclUpdate(UPD_CXX_ADDED_ANONYMOUS_NAMESPACE, D));
1355     }
1356   }
1357 }
1358 
1359 void ASTDeclWriter::VisitNamespaceAliasDecl(NamespaceAliasDecl *D) {
1360   VisitRedeclarable(D);
1361   VisitNamedDecl(D);
1362   Record.AddSourceLocation(D->getNamespaceLoc());
1363   Record.AddSourceLocation(D->getTargetNameLoc());
1364   Record.AddNestedNameSpecifierLoc(D->getQualifierLoc());
1365   Record.AddDeclRef(D->getNamespace());
1366   Code = serialization::DECL_NAMESPACE_ALIAS;
1367 }
1368 
1369 void ASTDeclWriter::VisitUsingDecl(UsingDecl *D) {
1370   VisitNamedDecl(D);
1371   Record.AddSourceLocation(D->getUsingLoc());
1372   Record.AddNestedNameSpecifierLoc(D->getQualifierLoc());
1373   Record.AddDeclarationNameLoc(D->DNLoc, D->getDeclName());
1374   Record.AddDeclRef(D->FirstUsingShadow.getPointer());
1375   Record.push_back(D->hasTypename());
1376   Record.AddDeclRef(Context.getInstantiatedFromUsingDecl(D));
1377   Code = serialization::DECL_USING;
1378 }
1379 
1380 void ASTDeclWriter::VisitUsingEnumDecl(UsingEnumDecl *D) {
1381   VisitNamedDecl(D);
1382   Record.AddSourceLocation(D->getUsingLoc());
1383   Record.AddSourceLocation(D->getEnumLoc());
1384   Record.AddTypeSourceInfo(D->getEnumType());
1385   Record.AddDeclRef(D->FirstUsingShadow.getPointer());
1386   Record.AddDeclRef(Context.getInstantiatedFromUsingEnumDecl(D));
1387   Code = serialization::DECL_USING_ENUM;
1388 }
1389 
1390 void ASTDeclWriter::VisitUsingPackDecl(UsingPackDecl *D) {
1391   Record.push_back(D->NumExpansions);
1392   VisitNamedDecl(D);
1393   Record.AddDeclRef(D->getInstantiatedFromUsingDecl());
1394   for (auto *E : D->expansions())
1395     Record.AddDeclRef(E);
1396   Code = serialization::DECL_USING_PACK;
1397 }
1398 
1399 void ASTDeclWriter::VisitUsingShadowDecl(UsingShadowDecl *D) {
1400   VisitRedeclarable(D);
1401   VisitNamedDecl(D);
1402   Record.AddDeclRef(D->getTargetDecl());
1403   Record.push_back(D->getIdentifierNamespace());
1404   Record.AddDeclRef(D->UsingOrNextShadow);
1405   Record.AddDeclRef(Context.getInstantiatedFromUsingShadowDecl(D));
1406 
1407   if (D->getDeclContext() == D->getLexicalDeclContext() &&
1408       D->getFirstDecl() == D->getMostRecentDecl() && !D->hasAttrs() &&
1409       !needsAnonymousDeclarationNumber(D) &&
1410       D->getDeclName().getNameKind() == DeclarationName::Identifier)
1411     AbbrevToUse = Writer.getDeclUsingShadowAbbrev();
1412 
1413   Code = serialization::DECL_USING_SHADOW;
1414 }
1415 
1416 void ASTDeclWriter::VisitConstructorUsingShadowDecl(
1417     ConstructorUsingShadowDecl *D) {
1418   VisitUsingShadowDecl(D);
1419   Record.AddDeclRef(D->NominatedBaseClassShadowDecl);
1420   Record.AddDeclRef(D->ConstructedBaseClassShadowDecl);
1421   Record.push_back(D->IsVirtual);
1422   Code = serialization::DECL_CONSTRUCTOR_USING_SHADOW;
1423 }
1424 
1425 void ASTDeclWriter::VisitUsingDirectiveDecl(UsingDirectiveDecl *D) {
1426   VisitNamedDecl(D);
1427   Record.AddSourceLocation(D->getUsingLoc());
1428   Record.AddSourceLocation(D->getNamespaceKeyLocation());
1429   Record.AddNestedNameSpecifierLoc(D->getQualifierLoc());
1430   Record.AddDeclRef(D->getNominatedNamespace());
1431   Record.AddDeclRef(dyn_cast<Decl>(D->getCommonAncestor()));
1432   Code = serialization::DECL_USING_DIRECTIVE;
1433 }
1434 
1435 void ASTDeclWriter::VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D) {
1436   VisitValueDecl(D);
1437   Record.AddSourceLocation(D->getUsingLoc());
1438   Record.AddNestedNameSpecifierLoc(D->getQualifierLoc());
1439   Record.AddDeclarationNameLoc(D->DNLoc, D->getDeclName());
1440   Record.AddSourceLocation(D->getEllipsisLoc());
1441   Code = serialization::DECL_UNRESOLVED_USING_VALUE;
1442 }
1443 
1444 void ASTDeclWriter::VisitUnresolvedUsingTypenameDecl(
1445                                                UnresolvedUsingTypenameDecl *D) {
1446   VisitTypeDecl(D);
1447   Record.AddSourceLocation(D->getTypenameLoc());
1448   Record.AddNestedNameSpecifierLoc(D->getQualifierLoc());
1449   Record.AddSourceLocation(D->getEllipsisLoc());
1450   Code = serialization::DECL_UNRESOLVED_USING_TYPENAME;
1451 }
1452 
1453 void ASTDeclWriter::VisitUnresolvedUsingIfExistsDecl(
1454     UnresolvedUsingIfExistsDecl *D) {
1455   VisitNamedDecl(D);
1456   Code = serialization::DECL_UNRESOLVED_USING_IF_EXISTS;
1457 }
1458 
1459 void ASTDeclWriter::VisitCXXRecordDecl(CXXRecordDecl *D) {
1460   VisitRecordDecl(D);
1461 
1462   enum {
1463     CXXRecNotTemplate = 0,
1464     CXXRecTemplate,
1465     CXXRecMemberSpecialization,
1466     CXXLambda
1467   };
1468   if (ClassTemplateDecl *TemplD = D->getDescribedClassTemplate()) {
1469     Record.push_back(CXXRecTemplate);
1470     Record.AddDeclRef(TemplD);
1471   } else if (MemberSpecializationInfo *MSInfo
1472                = D->getMemberSpecializationInfo()) {
1473     Record.push_back(CXXRecMemberSpecialization);
1474     Record.AddDeclRef(MSInfo->getInstantiatedFrom());
1475     Record.push_back(MSInfo->getTemplateSpecializationKind());
1476     Record.AddSourceLocation(MSInfo->getPointOfInstantiation());
1477   } else if (D->isLambda()) {
1478     // For a lambda, we need some information early for merging.
1479     Record.push_back(CXXLambda);
1480     if (auto *Context = D->getLambdaContextDecl()) {
1481       Record.AddDeclRef(Context);
1482       Record.push_back(D->getLambdaIndexInContext());
1483     } else {
1484       Record.push_back(0);
1485     }
1486   } else {
1487     Record.push_back(CXXRecNotTemplate);
1488   }
1489 
1490   Record.push_back(D->isThisDeclarationADefinition());
1491   if (D->isThisDeclarationADefinition())
1492     Record.AddCXXDefinitionData(D);
1493 
1494   // Store (what we currently believe to be) the key function to avoid
1495   // deserializing every method so we can compute it.
1496   if (D->isCompleteDefinition())
1497     Record.AddDeclRef(Context.getCurrentKeyFunction(D));
1498 
1499   Code = serialization::DECL_CXX_RECORD;
1500 }
1501 
1502 void ASTDeclWriter::VisitCXXMethodDecl(CXXMethodDecl *D) {
1503   VisitFunctionDecl(D);
1504   if (D->isCanonicalDecl()) {
1505     Record.push_back(D->size_overridden_methods());
1506     for (const CXXMethodDecl *MD : D->overridden_methods())
1507       Record.AddDeclRef(MD);
1508   } else {
1509     // We only need to record overridden methods once for the canonical decl.
1510     Record.push_back(0);
1511   }
1512 
1513   if (D->getDeclContext() == D->getLexicalDeclContext() &&
1514       D->getFirstDecl() == D->getMostRecentDecl() && !D->isInvalidDecl() &&
1515       !D->hasAttrs() && !D->isTopLevelDeclInObjCContainer() &&
1516       D->getDeclName().getNameKind() == DeclarationName::Identifier &&
1517       !D->shouldSkipCheckingODR() && !D->hasExtInfo() &&
1518       !D->isExplicitlyDefaulted()) {
1519     if (D->getTemplatedKind() == FunctionDecl::TK_NonTemplate ||
1520         D->getTemplatedKind() == FunctionDecl::TK_FunctionTemplate ||
1521         D->getTemplatedKind() == FunctionDecl::TK_MemberSpecialization ||
1522         D->getTemplatedKind() == FunctionDecl::TK_DependentNonTemplate)
1523       AbbrevToUse = Writer.getDeclCXXMethodAbbrev(D->getTemplatedKind());
1524     else if (D->getTemplatedKind() ==
1525              FunctionDecl::TK_FunctionTemplateSpecialization) {
1526       FunctionTemplateSpecializationInfo *FTSInfo =
1527           D->getTemplateSpecializationInfo();
1528 
1529       if (FTSInfo->TemplateArguments->size() == 1) {
1530         const TemplateArgument &TA = FTSInfo->TemplateArguments->get(0);
1531         if (TA.getKind() == TemplateArgument::Type &&
1532             !FTSInfo->TemplateArgumentsAsWritten &&
1533             !FTSInfo->getMemberSpecializationInfo())
1534           AbbrevToUse = Writer.getDeclCXXMethodAbbrev(D->getTemplatedKind());
1535       }
1536     } else if (D->getTemplatedKind() ==
1537                FunctionDecl::TK_DependentFunctionTemplateSpecialization) {
1538       DependentFunctionTemplateSpecializationInfo *DFTSInfo =
1539           D->getDependentSpecializationInfo();
1540       if (!DFTSInfo->TemplateArgumentsAsWritten)
1541         AbbrevToUse = Writer.getDeclCXXMethodAbbrev(D->getTemplatedKind());
1542     }
1543   }
1544 
1545   Code = serialization::DECL_CXX_METHOD;
1546 }
1547 
1548 void ASTDeclWriter::VisitCXXConstructorDecl(CXXConstructorDecl *D) {
1549   static_assert(DeclContext::NumCXXConstructorDeclBits == 64,
1550                 "You need to update the serializer after you change the "
1551                 "CXXConstructorDeclBits");
1552 
1553   Record.push_back(D->getTrailingAllocKind());
1554   addExplicitSpecifier(D->getExplicitSpecifier(), Record);
1555   if (auto Inherited = D->getInheritedConstructor()) {
1556     Record.AddDeclRef(Inherited.getShadowDecl());
1557     Record.AddDeclRef(Inherited.getConstructor());
1558   }
1559 
1560   VisitCXXMethodDecl(D);
1561   Code = serialization::DECL_CXX_CONSTRUCTOR;
1562 }
1563 
1564 void ASTDeclWriter::VisitCXXDestructorDecl(CXXDestructorDecl *D) {
1565   VisitCXXMethodDecl(D);
1566 
1567   Record.AddDeclRef(D->getOperatorDelete());
1568   if (D->getOperatorDelete())
1569     Record.AddStmt(D->getOperatorDeleteThisArg());
1570 
1571   Code = serialization::DECL_CXX_DESTRUCTOR;
1572 }
1573 
1574 void ASTDeclWriter::VisitCXXConversionDecl(CXXConversionDecl *D) {
1575   addExplicitSpecifier(D->getExplicitSpecifier(), Record);
1576   VisitCXXMethodDecl(D);
1577   Code = serialization::DECL_CXX_CONVERSION;
1578 }
1579 
1580 void ASTDeclWriter::VisitImportDecl(ImportDecl *D) {
1581   VisitDecl(D);
1582   Record.push_back(Writer.getSubmoduleID(D->getImportedModule()));
1583   ArrayRef<SourceLocation> IdentifierLocs = D->getIdentifierLocs();
1584   Record.push_back(!IdentifierLocs.empty());
1585   if (IdentifierLocs.empty()) {
1586     Record.AddSourceLocation(D->getEndLoc());
1587     Record.push_back(1);
1588   } else {
1589     for (unsigned I = 0, N = IdentifierLocs.size(); I != N; ++I)
1590       Record.AddSourceLocation(IdentifierLocs[I]);
1591     Record.push_back(IdentifierLocs.size());
1592   }
1593   // Note: the number of source locations must always be the last element in
1594   // the record.
1595   Code = serialization::DECL_IMPORT;
1596 }
1597 
1598 void ASTDeclWriter::VisitAccessSpecDecl(AccessSpecDecl *D) {
1599   VisitDecl(D);
1600   Record.AddSourceLocation(D->getColonLoc());
1601   Code = serialization::DECL_ACCESS_SPEC;
1602 }
1603 
1604 void ASTDeclWriter::VisitFriendDecl(FriendDecl *D) {
1605   // Record the number of friend type template parameter lists here
1606   // so as to simplify memory allocation during deserialization.
1607   Record.push_back(D->NumTPLists);
1608   VisitDecl(D);
1609   bool hasFriendDecl = D->Friend.is<NamedDecl*>();
1610   Record.push_back(hasFriendDecl);
1611   if (hasFriendDecl)
1612     Record.AddDeclRef(D->getFriendDecl());
1613   else
1614     Record.AddTypeSourceInfo(D->getFriendType());
1615   for (unsigned i = 0; i < D->NumTPLists; ++i)
1616     Record.AddTemplateParameterList(D->getFriendTypeTemplateParameterList(i));
1617   Record.AddDeclRef(D->getNextFriend());
1618   Record.push_back(D->UnsupportedFriend);
1619   Record.AddSourceLocation(D->FriendLoc);
1620   Code = serialization::DECL_FRIEND;
1621 }
1622 
1623 void ASTDeclWriter::VisitFriendTemplateDecl(FriendTemplateDecl *D) {
1624   VisitDecl(D);
1625   Record.push_back(D->getNumTemplateParameters());
1626   for (unsigned i = 0, e = D->getNumTemplateParameters(); i != e; ++i)
1627     Record.AddTemplateParameterList(D->getTemplateParameterList(i));
1628   Record.push_back(D->getFriendDecl() != nullptr);
1629   if (D->getFriendDecl())
1630     Record.AddDeclRef(D->getFriendDecl());
1631   else
1632     Record.AddTypeSourceInfo(D->getFriendType());
1633   Record.AddSourceLocation(D->getFriendLoc());
1634   Code = serialization::DECL_FRIEND_TEMPLATE;
1635 }
1636 
1637 void ASTDeclWriter::VisitTemplateDecl(TemplateDecl *D) {
1638   VisitNamedDecl(D);
1639 
1640   Record.AddTemplateParameterList(D->getTemplateParameters());
1641   Record.AddDeclRef(D->getTemplatedDecl());
1642 }
1643 
1644 void ASTDeclWriter::VisitConceptDecl(ConceptDecl *D) {
1645   VisitTemplateDecl(D);
1646   Record.AddStmt(D->getConstraintExpr());
1647   Code = serialization::DECL_CONCEPT;
1648 }
1649 
1650 void ASTDeclWriter::VisitImplicitConceptSpecializationDecl(
1651     ImplicitConceptSpecializationDecl *D) {
1652   Record.push_back(D->getTemplateArguments().size());
1653   VisitDecl(D);
1654   for (const TemplateArgument &Arg : D->getTemplateArguments())
1655     Record.AddTemplateArgument(Arg);
1656   Code = serialization::DECL_IMPLICIT_CONCEPT_SPECIALIZATION;
1657 }
1658 
1659 void ASTDeclWriter::VisitRequiresExprBodyDecl(RequiresExprBodyDecl *D) {
1660   Code = serialization::DECL_REQUIRES_EXPR_BODY;
1661 }
1662 
1663 void ASTDeclWriter::VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D) {
1664   VisitRedeclarable(D);
1665 
1666   // Emit data to initialize CommonOrPrev before VisitTemplateDecl so that
1667   // getCommonPtr() can be used while this is still initializing.
1668   if (D->isFirstDecl()) {
1669     // This declaration owns the 'common' pointer, so serialize that data now.
1670     Record.AddDeclRef(D->getInstantiatedFromMemberTemplate());
1671     if (D->getInstantiatedFromMemberTemplate())
1672       Record.push_back(D->isMemberSpecialization());
1673   }
1674 
1675   VisitTemplateDecl(D);
1676   Record.push_back(D->getIdentifierNamespace());
1677 }
1678 
1679 void ASTDeclWriter::VisitClassTemplateDecl(ClassTemplateDecl *D) {
1680   VisitRedeclarableTemplateDecl(D);
1681 
1682   if (D->isFirstDecl())
1683     AddTemplateSpecializations(D);
1684   Code = serialization::DECL_CLASS_TEMPLATE;
1685 }
1686 
1687 void ASTDeclWriter::VisitClassTemplateSpecializationDecl(
1688                                            ClassTemplateSpecializationDecl *D) {
1689   RegisterTemplateSpecialization(D->getSpecializedTemplate(), D);
1690 
1691   VisitCXXRecordDecl(D);
1692 
1693   llvm::PointerUnion<ClassTemplateDecl *,
1694                      ClassTemplatePartialSpecializationDecl *> InstFrom
1695     = D->getSpecializedTemplateOrPartial();
1696   if (Decl *InstFromD = InstFrom.dyn_cast<ClassTemplateDecl *>()) {
1697     Record.AddDeclRef(InstFromD);
1698   } else {
1699     Record.AddDeclRef(InstFrom.get<ClassTemplatePartialSpecializationDecl *>());
1700     Record.AddTemplateArgumentList(&D->getTemplateInstantiationArgs());
1701   }
1702 
1703   Record.AddTemplateArgumentList(&D->getTemplateArgs());
1704   Record.AddSourceLocation(D->getPointOfInstantiation());
1705   Record.push_back(D->getSpecializationKind());
1706   Record.push_back(D->isCanonicalDecl());
1707 
1708   if (D->isCanonicalDecl()) {
1709     // When reading, we'll add it to the folding set of the following template.
1710     Record.AddDeclRef(D->getSpecializedTemplate()->getCanonicalDecl());
1711   }
1712 
1713   // Explicit info.
1714   Record.AddTypeSourceInfo(D->getTypeAsWritten());
1715   if (D->getTypeAsWritten()) {
1716     Record.AddSourceLocation(D->getExternLoc());
1717     Record.AddSourceLocation(D->getTemplateKeywordLoc());
1718   }
1719 
1720   Code = serialization::DECL_CLASS_TEMPLATE_SPECIALIZATION;
1721 }
1722 
1723 void ASTDeclWriter::VisitClassTemplatePartialSpecializationDecl(
1724                                     ClassTemplatePartialSpecializationDecl *D) {
1725   Record.AddTemplateParameterList(D->getTemplateParameters());
1726   Record.AddASTTemplateArgumentListInfo(D->getTemplateArgsAsWritten());
1727 
1728   VisitClassTemplateSpecializationDecl(D);
1729 
1730   // These are read/set from/to the first declaration.
1731   if (D->getPreviousDecl() == nullptr) {
1732     Record.AddDeclRef(D->getInstantiatedFromMember());
1733     Record.push_back(D->isMemberSpecialization());
1734   }
1735 
1736   Code = serialization::DECL_CLASS_TEMPLATE_PARTIAL_SPECIALIZATION;
1737 }
1738 
1739 void ASTDeclWriter::VisitVarTemplateDecl(VarTemplateDecl *D) {
1740   VisitRedeclarableTemplateDecl(D);
1741 
1742   if (D->isFirstDecl())
1743     AddTemplateSpecializations(D);
1744   Code = serialization::DECL_VAR_TEMPLATE;
1745 }
1746 
1747 void ASTDeclWriter::VisitVarTemplateSpecializationDecl(
1748     VarTemplateSpecializationDecl *D) {
1749   RegisterTemplateSpecialization(D->getSpecializedTemplate(), D);
1750 
1751   llvm::PointerUnion<VarTemplateDecl *, VarTemplatePartialSpecializationDecl *>
1752   InstFrom = D->getSpecializedTemplateOrPartial();
1753   if (Decl *InstFromD = InstFrom.dyn_cast<VarTemplateDecl *>()) {
1754     Record.AddDeclRef(InstFromD);
1755   } else {
1756     Record.AddDeclRef(InstFrom.get<VarTemplatePartialSpecializationDecl *>());
1757     Record.AddTemplateArgumentList(&D->getTemplateInstantiationArgs());
1758   }
1759 
1760   // Explicit info.
1761   Record.AddTypeSourceInfo(D->getTypeAsWritten());
1762   if (D->getTypeAsWritten()) {
1763     Record.AddSourceLocation(D->getExternLoc());
1764     Record.AddSourceLocation(D->getTemplateKeywordLoc());
1765   }
1766 
1767   Record.AddTemplateArgumentList(&D->getTemplateArgs());
1768   Record.AddSourceLocation(D->getPointOfInstantiation());
1769   Record.push_back(D->getSpecializationKind());
1770   Record.push_back(D->IsCompleteDefinition);
1771 
1772   VisitVarDecl(D);
1773 
1774   Record.push_back(D->isCanonicalDecl());
1775 
1776   if (D->isCanonicalDecl()) {
1777     // When reading, we'll add it to the folding set of the following template.
1778     Record.AddDeclRef(D->getSpecializedTemplate()->getCanonicalDecl());
1779   }
1780 
1781   Code = serialization::DECL_VAR_TEMPLATE_SPECIALIZATION;
1782 }
1783 
1784 void ASTDeclWriter::VisitVarTemplatePartialSpecializationDecl(
1785     VarTemplatePartialSpecializationDecl *D) {
1786   Record.AddTemplateParameterList(D->getTemplateParameters());
1787   Record.AddASTTemplateArgumentListInfo(D->getTemplateArgsAsWritten());
1788 
1789   VisitVarTemplateSpecializationDecl(D);
1790 
1791   // These are read/set from/to the first declaration.
1792   if (D->getPreviousDecl() == nullptr) {
1793     Record.AddDeclRef(D->getInstantiatedFromMember());
1794     Record.push_back(D->isMemberSpecialization());
1795   }
1796 
1797   Code = serialization::DECL_VAR_TEMPLATE_PARTIAL_SPECIALIZATION;
1798 }
1799 
1800 void ASTDeclWriter::VisitFunctionTemplateDecl(FunctionTemplateDecl *D) {
1801   VisitRedeclarableTemplateDecl(D);
1802 
1803   if (D->isFirstDecl())
1804     AddTemplateSpecializations(D);
1805   Code = serialization::DECL_FUNCTION_TEMPLATE;
1806 }
1807 
1808 void ASTDeclWriter::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
1809   Record.push_back(D->hasTypeConstraint());
1810   VisitTypeDecl(D);
1811 
1812   Record.push_back(D->wasDeclaredWithTypename());
1813 
1814   const TypeConstraint *TC = D->getTypeConstraint();
1815   assert((bool)TC == D->hasTypeConstraint());
1816   if (TC) {
1817     auto *CR = TC->getConceptReference();
1818     Record.push_back(CR != nullptr);
1819     if (CR)
1820       Record.AddConceptReference(CR);
1821     Record.AddStmt(TC->getImmediatelyDeclaredConstraint());
1822     Record.push_back(D->isExpandedParameterPack());
1823     if (D->isExpandedParameterPack())
1824       Record.push_back(D->getNumExpansionParameters());
1825   }
1826 
1827   bool OwnsDefaultArg = D->hasDefaultArgument() &&
1828                         !D->defaultArgumentWasInherited();
1829   Record.push_back(OwnsDefaultArg);
1830   if (OwnsDefaultArg)
1831     Record.AddTypeSourceInfo(D->getDefaultArgumentInfo());
1832 
1833   if (!TC && !OwnsDefaultArg &&
1834       D->getDeclContext() == D->getLexicalDeclContext() &&
1835       !D->isInvalidDecl() && !D->hasAttrs() &&
1836       !D->isTopLevelDeclInObjCContainer() && !D->isImplicit() &&
1837       D->getDeclName().getNameKind() == DeclarationName::Identifier)
1838     AbbrevToUse = Writer.getDeclTemplateTypeParmAbbrev();
1839 
1840   Code = serialization::DECL_TEMPLATE_TYPE_PARM;
1841 }
1842 
1843 void ASTDeclWriter::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {
1844   // For an expanded parameter pack, record the number of expansion types here
1845   // so that it's easier for deserialization to allocate the right amount of
1846   // memory.
1847   Expr *TypeConstraint = D->getPlaceholderTypeConstraint();
1848   Record.push_back(!!TypeConstraint);
1849   if (D->isExpandedParameterPack())
1850     Record.push_back(D->getNumExpansionTypes());
1851 
1852   VisitDeclaratorDecl(D);
1853   // TemplateParmPosition.
1854   Record.push_back(D->getDepth());
1855   Record.push_back(D->getPosition());
1856   if (TypeConstraint)
1857     Record.AddStmt(TypeConstraint);
1858 
1859   if (D->isExpandedParameterPack()) {
1860     for (unsigned I = 0, N = D->getNumExpansionTypes(); I != N; ++I) {
1861       Record.AddTypeRef(D->getExpansionType(I));
1862       Record.AddTypeSourceInfo(D->getExpansionTypeSourceInfo(I));
1863     }
1864 
1865     Code = serialization::DECL_EXPANDED_NON_TYPE_TEMPLATE_PARM_PACK;
1866   } else {
1867     // Rest of NonTypeTemplateParmDecl.
1868     Record.push_back(D->isParameterPack());
1869     bool OwnsDefaultArg = D->hasDefaultArgument() &&
1870                           !D->defaultArgumentWasInherited();
1871     Record.push_back(OwnsDefaultArg);
1872     if (OwnsDefaultArg)
1873       Record.AddStmt(D->getDefaultArgument());
1874     Code = serialization::DECL_NON_TYPE_TEMPLATE_PARM;
1875   }
1876 }
1877 
1878 void ASTDeclWriter::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {
1879   // For an expanded parameter pack, record the number of expansion types here
1880   // so that it's easier for deserialization to allocate the right amount of
1881   // memory.
1882   if (D->isExpandedParameterPack())
1883     Record.push_back(D->getNumExpansionTemplateParameters());
1884 
1885   VisitTemplateDecl(D);
1886   // TemplateParmPosition.
1887   Record.push_back(D->getDepth());
1888   Record.push_back(D->getPosition());
1889 
1890   if (D->isExpandedParameterPack()) {
1891     for (unsigned I = 0, N = D->getNumExpansionTemplateParameters();
1892          I != N; ++I)
1893       Record.AddTemplateParameterList(D->getExpansionTemplateParameters(I));
1894     Code = serialization::DECL_EXPANDED_TEMPLATE_TEMPLATE_PARM_PACK;
1895   } else {
1896     // Rest of TemplateTemplateParmDecl.
1897     Record.push_back(D->isParameterPack());
1898     bool OwnsDefaultArg = D->hasDefaultArgument() &&
1899                           !D->defaultArgumentWasInherited();
1900     Record.push_back(OwnsDefaultArg);
1901     if (OwnsDefaultArg)
1902       Record.AddTemplateArgumentLoc(D->getDefaultArgument());
1903     Code = serialization::DECL_TEMPLATE_TEMPLATE_PARM;
1904   }
1905 }
1906 
1907 void ASTDeclWriter::VisitTypeAliasTemplateDecl(TypeAliasTemplateDecl *D) {
1908   VisitRedeclarableTemplateDecl(D);
1909   Code = serialization::DECL_TYPE_ALIAS_TEMPLATE;
1910 }
1911 
1912 void ASTDeclWriter::VisitStaticAssertDecl(StaticAssertDecl *D) {
1913   VisitDecl(D);
1914   Record.AddStmt(D->getAssertExpr());
1915   Record.push_back(D->isFailed());
1916   Record.AddStmt(D->getMessage());
1917   Record.AddSourceLocation(D->getRParenLoc());
1918   Code = serialization::DECL_STATIC_ASSERT;
1919 }
1920 
1921 /// Emit the DeclContext part of a declaration context decl.
1922 void ASTDeclWriter::VisitDeclContext(DeclContext *DC) {
1923   static_assert(DeclContext::NumDeclContextBits == 13,
1924                 "You need to update the serializer after you change the "
1925                 "DeclContextBits");
1926 
1927   Record.AddOffset(Writer.WriteDeclContextLexicalBlock(Context, DC));
1928   Record.AddOffset(Writer.WriteDeclContextVisibleBlock(Context, DC));
1929 }
1930 
1931 const Decl *ASTWriter::getFirstLocalDecl(const Decl *D) {
1932   assert(IsLocalDecl(D) && "expected a local declaration");
1933 
1934   const Decl *Canon = D->getCanonicalDecl();
1935   if (IsLocalDecl(Canon))
1936     return Canon;
1937 
1938   const Decl *&CacheEntry = FirstLocalDeclCache[Canon];
1939   if (CacheEntry)
1940     return CacheEntry;
1941 
1942   for (const Decl *Redecl = D; Redecl; Redecl = Redecl->getPreviousDecl())
1943     if (IsLocalDecl(Redecl))
1944       D = Redecl;
1945   return CacheEntry = D;
1946 }
1947 
1948 template <typename T>
1949 void ASTDeclWriter::VisitRedeclarable(Redeclarable<T> *D) {
1950   T *First = D->getFirstDecl();
1951   T *MostRecent = First->getMostRecentDecl();
1952   T *DAsT = static_cast<T *>(D);
1953   if (MostRecent != First) {
1954     assert(isRedeclarableDeclKind(DAsT->getKind()) &&
1955            "Not considered redeclarable?");
1956 
1957     Record.AddDeclRef(First);
1958 
1959     // Write out a list of local redeclarations of this declaration if it's the
1960     // first local declaration in the chain.
1961     const Decl *FirstLocal = Writer.getFirstLocalDecl(DAsT);
1962     if (DAsT == FirstLocal) {
1963       // Emit a list of all imported first declarations so that we can be sure
1964       // that all redeclarations visible to this module are before D in the
1965       // redecl chain.
1966       unsigned I = Record.size();
1967       Record.push_back(0);
1968       if (Writer.Chain)
1969         AddFirstDeclFromEachModule(DAsT, /*IncludeLocal*/false);
1970       // This is the number of imported first declarations + 1.
1971       Record[I] = Record.size() - I;
1972 
1973       // Collect the set of local redeclarations of this declaration, from
1974       // newest to oldest.
1975       ASTWriter::RecordData LocalRedecls;
1976       ASTRecordWriter LocalRedeclWriter(Record, LocalRedecls);
1977       for (const Decl *Prev = FirstLocal->getMostRecentDecl();
1978            Prev != FirstLocal; Prev = Prev->getPreviousDecl())
1979         if (!Prev->isFromASTFile())
1980           LocalRedeclWriter.AddDeclRef(Prev);
1981 
1982       // If we have any redecls, write them now as a separate record preceding
1983       // the declaration itself.
1984       if (LocalRedecls.empty())
1985         Record.push_back(0);
1986       else
1987         Record.AddOffset(LocalRedeclWriter.Emit(LOCAL_REDECLARATIONS));
1988     } else {
1989       Record.push_back(0);
1990       Record.AddDeclRef(FirstLocal);
1991     }
1992 
1993     // Make sure that we serialize both the previous and the most-recent
1994     // declarations, which (transitively) ensures that all declarations in the
1995     // chain get serialized.
1996     //
1997     // FIXME: This is not correct; when we reach an imported declaration we
1998     // won't emit its previous declaration.
1999     (void)Writer.GetDeclRef(D->getPreviousDecl());
2000     (void)Writer.GetDeclRef(MostRecent);
2001   } else {
2002     // We use the sentinel value 0 to indicate an only declaration.
2003     Record.push_back(0);
2004   }
2005 }
2006 
2007 void ASTDeclWriter::VisitHLSLBufferDecl(HLSLBufferDecl *D) {
2008   VisitNamedDecl(D);
2009   VisitDeclContext(D);
2010   Record.push_back(D->isCBuffer());
2011   Record.AddSourceLocation(D->getLocStart());
2012   Record.AddSourceLocation(D->getLBraceLoc());
2013   Record.AddSourceLocation(D->getRBraceLoc());
2014 
2015   Code = serialization::DECL_HLSL_BUFFER;
2016 }
2017 
2018 void ASTDeclWriter::VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D) {
2019   Record.writeOMPChildren(D->Data);
2020   VisitDecl(D);
2021   Code = serialization::DECL_OMP_THREADPRIVATE;
2022 }
2023 
2024 void ASTDeclWriter::VisitOMPAllocateDecl(OMPAllocateDecl *D) {
2025   Record.writeOMPChildren(D->Data);
2026   VisitDecl(D);
2027   Code = serialization::DECL_OMP_ALLOCATE;
2028 }
2029 
2030 void ASTDeclWriter::VisitOMPRequiresDecl(OMPRequiresDecl *D) {
2031   Record.writeOMPChildren(D->Data);
2032   VisitDecl(D);
2033   Code = serialization::DECL_OMP_REQUIRES;
2034 }
2035 
2036 void ASTDeclWriter::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
2037   static_assert(DeclContext::NumOMPDeclareReductionDeclBits == 15,
2038                 "You need to update the serializer after you change the "
2039                 "NumOMPDeclareReductionDeclBits");
2040 
2041   VisitValueDecl(D);
2042   Record.AddSourceLocation(D->getBeginLoc());
2043   Record.AddStmt(D->getCombinerIn());
2044   Record.AddStmt(D->getCombinerOut());
2045   Record.AddStmt(D->getCombiner());
2046   Record.AddStmt(D->getInitOrig());
2047   Record.AddStmt(D->getInitPriv());
2048   Record.AddStmt(D->getInitializer());
2049   Record.push_back(llvm::to_underlying(D->getInitializerKind()));
2050   Record.AddDeclRef(D->getPrevDeclInScope());
2051   Code = serialization::DECL_OMP_DECLARE_REDUCTION;
2052 }
2053 
2054 void ASTDeclWriter::VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D) {
2055   Record.writeOMPChildren(D->Data);
2056   VisitValueDecl(D);
2057   Record.AddDeclarationName(D->getVarName());
2058   Record.AddDeclRef(D->getPrevDeclInScope());
2059   Code = serialization::DECL_OMP_DECLARE_MAPPER;
2060 }
2061 
2062 void ASTDeclWriter::VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D) {
2063   VisitVarDecl(D);
2064   Code = serialization::DECL_OMP_CAPTUREDEXPR;
2065 }
2066 
2067 //===----------------------------------------------------------------------===//
2068 // ASTWriter Implementation
2069 //===----------------------------------------------------------------------===//
2070 
2071 namespace {
2072 template <FunctionDecl::TemplatedKind Kind>
2073 std::shared_ptr<llvm::BitCodeAbbrev>
2074 getFunctionDeclAbbrev(serialization::DeclCode Code) {
2075   using namespace llvm;
2076 
2077   auto Abv = std::make_shared<BitCodeAbbrev>();
2078   Abv->Add(BitCodeAbbrevOp(Code));
2079   // RedeclarableDecl
2080   Abv->Add(BitCodeAbbrevOp(0)); // CanonicalDecl
2081   Abv->Add(BitCodeAbbrevOp(Kind));
2082   if constexpr (Kind == FunctionDecl::TK_NonTemplate) {
2083 
2084   } else if constexpr (Kind == FunctionDecl::TK_FunctionTemplate) {
2085     // DescribedFunctionTemplate
2086     Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));
2087   } else if constexpr (Kind == FunctionDecl::TK_DependentNonTemplate) {
2088     // Instantiated From Decl
2089     Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));
2090   } else if constexpr (Kind == FunctionDecl::TK_MemberSpecialization) {
2091     Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // InstantiatedFrom
2092     Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2093                              3)); // TemplateSpecializationKind
2094     Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Specialized Location
2095   } else if constexpr (Kind ==
2096                        FunctionDecl::TK_FunctionTemplateSpecialization) {
2097     Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Template
2098     Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2099                              3)); // TemplateSpecializationKind
2100     Abv->Add(BitCodeAbbrevOp(1)); // Template Argument Size
2101     Abv->Add(BitCodeAbbrevOp(TemplateArgument::Type)); // Template Argument Kind
2102     Abv->Add(
2103         BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Template Argument Type
2104     Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Is Defaulted
2105     Abv->Add(BitCodeAbbrevOp(0)); // TemplateArgumentsAsWritten
2106     Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SourceLocation
2107     Abv->Add(BitCodeAbbrevOp(0));
2108     Abv->Add(
2109         BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Canonical Decl of template
2110   } else if constexpr (Kind == FunctionDecl::
2111                                    TK_DependentFunctionTemplateSpecialization) {
2112     // Candidates of specialization
2113     Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
2114     Abv->Add(BitCodeAbbrevOp(0)); // TemplateArgumentsAsWritten
2115   } else {
2116     llvm_unreachable("Unknown templated kind?");
2117   }
2118   // Decl
2119   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2120                            8)); // Packed DeclBits: ModuleOwnershipKind,
2121                                 // isUsed, isReferenced,  AccessSpecifier,
2122                                 // isImplicit
2123                                 //
2124                                 // The following bits should be 0:
2125                                 // HasStandaloneLexicalDC, HasAttrs,
2126                                 // TopLevelDeclInObjCContainer,
2127                                 // isInvalidDecl
2128   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
2129   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SubmoduleID
2130   // NamedDecl
2131   Abv->Add(BitCodeAbbrevOp(DeclarationName::Identifier)); // NameKind
2132   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));     // Identifier
2133   Abv->Add(BitCodeAbbrevOp(0));                           // AnonDeclNumber
2134   // ValueDecl
2135   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2136   // DeclaratorDecl
2137   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // InnerLocStart
2138   Abv->Add(BitCodeAbbrevOp(0));                       // HasExtInfo
2139   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // TSIType
2140   // FunctionDecl
2141   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 11)); // IDNS
2142   Abv->Add(BitCodeAbbrevOp(
2143       BitCodeAbbrevOp::Fixed,
2144       28)); // Packed Function Bits: StorageClass, Inline, InlineSpecified,
2145             // VirtualAsWritten, Pure, HasInheritedProto, HasWrittenProto,
2146             // Deleted, Trivial, TrivialForCall, Defaulted, ExplicitlyDefaulted,
2147             // IsIneligibleOrNotSelected, ImplicitReturnZero, Constexpr,
2148             // UsesSEHTry, SkippedBody, MultiVersion, LateParsed,
2149             // FriendConstraintRefersToEnclosingTemplate, Linkage,
2150             // ShouldSkipCheckingODR
2151   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));    // LocEnd
2152   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 32)); // ODRHash
2153   // This Array slurps the rest of the record. Fortunately we want to encode
2154   // (nearly) all the remaining (variable number of) fields in the same way.
2155   //
2156   // This is:
2157   //         NumParams and Params[] from FunctionDecl, and
2158   //         NumOverriddenMethods, OverriddenMethods[] from CXXMethodDecl.
2159   //
2160   //  Add an AbbrevOp for 'size then elements' and use it here.
2161   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
2162   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));
2163   return Abv;
2164 }
2165 
2166 template <FunctionDecl::TemplatedKind Kind>
2167 std::shared_ptr<llvm::BitCodeAbbrev> getCXXMethodAbbrev() {
2168   return getFunctionDeclAbbrev<Kind>(serialization::DECL_CXX_METHOD);
2169 }
2170 } // namespace
2171 
2172 void ASTWriter::WriteDeclAbbrevs() {
2173   using namespace llvm;
2174 
2175   std::shared_ptr<BitCodeAbbrev> Abv;
2176 
2177   // Abbreviation for DECL_FIELD
2178   Abv = std::make_shared<BitCodeAbbrev>();
2179   Abv->Add(BitCodeAbbrevOp(serialization::DECL_FIELD));
2180   // Decl
2181   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2182                            7)); // Packed DeclBits: ModuleOwnershipKind,
2183                                 // isUsed, isReferenced,  AccessSpecifier,
2184                                 //
2185                                 // The following bits should be 0:
2186                                 // isImplicit, HasStandaloneLexicalDC, HasAttrs,
2187                                 // TopLevelDeclInObjCContainer,
2188                                 // isInvalidDecl
2189   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
2190   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SubmoduleID
2191   // NamedDecl
2192   Abv->Add(BitCodeAbbrevOp(0));                       // NameKind = Identifier
2193   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Name
2194   Abv->Add(BitCodeAbbrevOp(0));                       // AnonDeclNumber
2195   // ValueDecl
2196   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2197   // DeclaratorDecl
2198   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // InnerStartLoc
2199   Abv->Add(BitCodeAbbrevOp(0));                       // hasExtInfo
2200   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // TSIType
2201   // FieldDecl
2202   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isMutable
2203   Abv->Add(BitCodeAbbrevOp(0));                       // StorageKind
2204   // Type Source Info
2205   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
2206   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // TypeLoc
2207   DeclFieldAbbrev = Stream.EmitAbbrev(std::move(Abv));
2208 
2209   // Abbreviation for DECL_OBJC_IVAR
2210   Abv = std::make_shared<BitCodeAbbrev>();
2211   Abv->Add(BitCodeAbbrevOp(serialization::DECL_OBJC_IVAR));
2212   // Decl
2213   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2214                            12)); // Packed DeclBits: HasStandaloneLexicalDC,
2215                                  // isInvalidDecl, HasAttrs, isImplicit, isUsed,
2216                                  // isReferenced, TopLevelDeclInObjCContainer,
2217                                  // AccessSpecifier, ModuleOwnershipKind
2218   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
2219   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SubmoduleID
2220   // NamedDecl
2221   Abv->Add(BitCodeAbbrevOp(0));                       // NameKind = Identifier
2222   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Name
2223   Abv->Add(BitCodeAbbrevOp(0));                       // AnonDeclNumber
2224   // ValueDecl
2225   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2226   // DeclaratorDecl
2227   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // InnerStartLoc
2228   Abv->Add(BitCodeAbbrevOp(0));                       // hasExtInfo
2229   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // TSIType
2230   // FieldDecl
2231   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isMutable
2232   Abv->Add(BitCodeAbbrevOp(0));                       // InitStyle
2233   // ObjC Ivar
2234   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // getAccessControl
2235   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // getSynthesize
2236   // Type Source Info
2237   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
2238   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // TypeLoc
2239   DeclObjCIvarAbbrev = Stream.EmitAbbrev(std::move(Abv));
2240 
2241   // Abbreviation for DECL_ENUM
2242   Abv = std::make_shared<BitCodeAbbrev>();
2243   Abv->Add(BitCodeAbbrevOp(serialization::DECL_ENUM));
2244   // Redeclarable
2245   Abv->Add(BitCodeAbbrevOp(0));                       // No redeclaration
2246   // Decl
2247   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2248                            7)); // Packed DeclBits: ModuleOwnershipKind,
2249                                 // isUsed, isReferenced,  AccessSpecifier,
2250                                 //
2251                                 // The following bits should be 0:
2252                                 // isImplicit, HasStandaloneLexicalDC, HasAttrs,
2253                                 // TopLevelDeclInObjCContainer,
2254                                 // isInvalidDecl
2255   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
2256   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SubmoduleID
2257   // NamedDecl
2258   Abv->Add(BitCodeAbbrevOp(0));                       // NameKind = Identifier
2259   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Name
2260   Abv->Add(BitCodeAbbrevOp(0));                       // AnonDeclNumber
2261   // TypeDecl
2262   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2263   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type Ref
2264   // TagDecl
2265   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // IdentifierNamespace
2266   Abv->Add(BitCodeAbbrevOp(
2267       BitCodeAbbrevOp::Fixed,
2268       9)); // Packed Tag Decl Bits: getTagKind, isCompleteDefinition,
2269            // EmbeddedInDeclarator, IsFreeStanding,
2270            // isCompleteDefinitionRequired, ExtInfoKind
2271   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // SourceLocation
2272   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // SourceLocation
2273   // EnumDecl
2274   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // AddTypeRef
2275   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // IntegerType
2276   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // getPromotionType
2277   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 20)); // Enum Decl Bits
2278   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 32));// ODRHash
2279   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // InstantiatedMembEnum
2280   // DC
2281   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // LexicalOffset
2282   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // VisibleOffset
2283   DeclEnumAbbrev = Stream.EmitAbbrev(std::move(Abv));
2284 
2285   // Abbreviation for DECL_RECORD
2286   Abv = std::make_shared<BitCodeAbbrev>();
2287   Abv->Add(BitCodeAbbrevOp(serialization::DECL_RECORD));
2288   // Redeclarable
2289   Abv->Add(BitCodeAbbrevOp(0));                       // No redeclaration
2290   // Decl
2291   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2292                            7)); // Packed DeclBits: ModuleOwnershipKind,
2293                                 // isUsed, isReferenced,  AccessSpecifier,
2294                                 //
2295                                 // The following bits should be 0:
2296                                 // isImplicit, HasStandaloneLexicalDC, HasAttrs,
2297                                 // TopLevelDeclInObjCContainer,
2298                                 // isInvalidDecl
2299   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
2300   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SubmoduleID
2301   // NamedDecl
2302   Abv->Add(BitCodeAbbrevOp(0));                       // NameKind = Identifier
2303   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Name
2304   Abv->Add(BitCodeAbbrevOp(0));                       // AnonDeclNumber
2305   // TypeDecl
2306   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2307   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type Ref
2308   // TagDecl
2309   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // IdentifierNamespace
2310   Abv->Add(BitCodeAbbrevOp(
2311       BitCodeAbbrevOp::Fixed,
2312       9)); // Packed Tag Decl Bits: getTagKind, isCompleteDefinition,
2313            // EmbeddedInDeclarator, IsFreeStanding,
2314            // isCompleteDefinitionRequired, ExtInfoKind
2315   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // SourceLocation
2316   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // SourceLocation
2317   // RecordDecl
2318   Abv->Add(BitCodeAbbrevOp(
2319       BitCodeAbbrevOp::Fixed,
2320       13)); // Packed Record Decl Bits: FlexibleArrayMember,
2321             // AnonymousStructUnion, hasObjectMember, hasVolatileMember,
2322             // isNonTrivialToPrimitiveDefaultInitialize,
2323             // isNonTrivialToPrimitiveCopy, isNonTrivialToPrimitiveDestroy,
2324             // hasNonTrivialToPrimitiveDefaultInitializeCUnion,
2325             // hasNonTrivialToPrimitiveDestructCUnion,
2326             // hasNonTrivialToPrimitiveCopyCUnion, isParamDestroyedInCallee,
2327             // getArgPassingRestrictions
2328   // ODRHash
2329   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 26));
2330 
2331   // DC
2332   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // LexicalOffset
2333   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // VisibleOffset
2334   DeclRecordAbbrev = Stream.EmitAbbrev(std::move(Abv));
2335 
2336   // Abbreviation for DECL_PARM_VAR
2337   Abv = std::make_shared<BitCodeAbbrev>();
2338   Abv->Add(BitCodeAbbrevOp(serialization::DECL_PARM_VAR));
2339   // Redeclarable
2340   Abv->Add(BitCodeAbbrevOp(0));                       // No redeclaration
2341   // Decl
2342   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2343                            8)); // Packed DeclBits: ModuleOwnershipKind, isUsed,
2344                                 // isReferenced, AccessSpecifier,
2345                                 // HasStandaloneLexicalDC, HasAttrs, isImplicit,
2346                                 // TopLevelDeclInObjCContainer,
2347                                 // isInvalidDecl,
2348   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
2349   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SubmoduleID
2350   // NamedDecl
2351   Abv->Add(BitCodeAbbrevOp(0));                       // NameKind = Identifier
2352   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Name
2353   Abv->Add(BitCodeAbbrevOp(0));                       // AnonDeclNumber
2354   // ValueDecl
2355   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2356   // DeclaratorDecl
2357   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // InnerStartLoc
2358   Abv->Add(BitCodeAbbrevOp(0));                       // hasExtInfo
2359   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // TSIType
2360   // VarDecl
2361   Abv->Add(
2362       BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2363                       12)); // Packed Var Decl bits: SClass, TSCSpec, InitStyle,
2364                             // isARCPseudoStrong, Linkage, ModulesCodegen
2365   Abv->Add(BitCodeAbbrevOp(0));                          // VarKind (local enum)
2366   // ParmVarDecl
2367   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // ScopeIndex
2368   Abv->Add(BitCodeAbbrevOp(
2369       BitCodeAbbrevOp::Fixed,
2370       19)); // Packed Parm Var Decl bits: IsObjCMethodParameter, ScopeDepth,
2371             // ObjCDeclQualifier, KNRPromoted,
2372             // HasInheritedDefaultArg, HasUninstantiatedDefaultArg
2373   // Type Source Info
2374   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
2375   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // TypeLoc
2376   DeclParmVarAbbrev = Stream.EmitAbbrev(std::move(Abv));
2377 
2378   // Abbreviation for DECL_TYPEDEF
2379   Abv = std::make_shared<BitCodeAbbrev>();
2380   Abv->Add(BitCodeAbbrevOp(serialization::DECL_TYPEDEF));
2381   // Redeclarable
2382   Abv->Add(BitCodeAbbrevOp(0));                       // No redeclaration
2383   // Decl
2384   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2385                            7)); // Packed DeclBits: ModuleOwnershipKind,
2386                                 // isReferenced, isUsed, AccessSpecifier. Other
2387                                 // higher bits should be 0: isImplicit,
2388                                 // HasStandaloneLexicalDC, HasAttrs,
2389                                 // TopLevelDeclInObjCContainer, isInvalidDecl
2390   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
2391   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SubmoduleID
2392   // NamedDecl
2393   Abv->Add(BitCodeAbbrevOp(0));                       // NameKind = Identifier
2394   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Name
2395   Abv->Add(BitCodeAbbrevOp(0));                       // AnonDeclNumber
2396   // TypeDecl
2397   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2398   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type Ref
2399   // TypedefDecl
2400   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
2401   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // TypeLoc
2402   DeclTypedefAbbrev = Stream.EmitAbbrev(std::move(Abv));
2403 
2404   // Abbreviation for DECL_VAR
2405   Abv = std::make_shared<BitCodeAbbrev>();
2406   Abv->Add(BitCodeAbbrevOp(serialization::DECL_VAR));
2407   // Redeclarable
2408   Abv->Add(BitCodeAbbrevOp(0));                       // No redeclaration
2409   // Decl
2410   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2411                            12)); // Packed DeclBits: HasStandaloneLexicalDC,
2412                                  // isInvalidDecl, HasAttrs, isImplicit, isUsed,
2413                                  // isReferenced, TopLevelDeclInObjCContainer,
2414                                  // AccessSpecifier, ModuleOwnershipKind
2415   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
2416   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SubmoduleID
2417   // NamedDecl
2418   Abv->Add(BitCodeAbbrevOp(0));                       // NameKind = Identifier
2419   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Name
2420   Abv->Add(BitCodeAbbrevOp(0));                       // AnonDeclNumber
2421   // ValueDecl
2422   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2423   // DeclaratorDecl
2424   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // InnerStartLoc
2425   Abv->Add(BitCodeAbbrevOp(0));                       // hasExtInfo
2426   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // TSIType
2427   // VarDecl
2428   Abv->Add(BitCodeAbbrevOp(
2429       BitCodeAbbrevOp::Fixed,
2430       21)); // Packed Var Decl bits:  Linkage, ModulesCodegen,
2431             // SClass, TSCSpec, InitStyle,
2432             // isARCPseudoStrong, IsThisDeclarationADemotedDefinition,
2433             // isExceptionVariable, isNRVOVariable, isCXXForRangeDecl,
2434             // isInline, isInlineSpecified, isConstexpr,
2435             // isInitCapture, isPrevDeclInSameScope,
2436             // EscapingByref, HasDeducedType, ImplicitParamKind, isObjCForDecl
2437   Abv->Add(BitCodeAbbrevOp(0));                         // VarKind (local enum)
2438   // Type Source Info
2439   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
2440   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // TypeLoc
2441   DeclVarAbbrev = Stream.EmitAbbrev(std::move(Abv));
2442 
2443   // Abbreviation for DECL_CXX_METHOD
2444   DeclCXXMethodAbbrev =
2445       Stream.EmitAbbrev(getCXXMethodAbbrev<FunctionDecl::TK_NonTemplate>());
2446   DeclTemplateCXXMethodAbbrev = Stream.EmitAbbrev(
2447       getCXXMethodAbbrev<FunctionDecl::TK_FunctionTemplate>());
2448   DeclDependentNonTemplateCXXMethodAbbrev = Stream.EmitAbbrev(
2449       getCXXMethodAbbrev<FunctionDecl::TK_DependentNonTemplate>());
2450   DeclMemberSpecializedCXXMethodAbbrev = Stream.EmitAbbrev(
2451       getCXXMethodAbbrev<FunctionDecl::TK_MemberSpecialization>());
2452   DeclTemplateSpecializedCXXMethodAbbrev = Stream.EmitAbbrev(
2453       getCXXMethodAbbrev<FunctionDecl::TK_FunctionTemplateSpecialization>());
2454   DeclDependentSpecializationCXXMethodAbbrev = Stream.EmitAbbrev(
2455       getCXXMethodAbbrev<
2456           FunctionDecl::TK_DependentFunctionTemplateSpecialization>());
2457 
2458   // Abbreviation for DECL_TEMPLATE_TYPE_PARM
2459   Abv = std::make_shared<BitCodeAbbrev>();
2460   Abv->Add(BitCodeAbbrevOp(serialization::DECL_TEMPLATE_TYPE_PARM));
2461   Abv->Add(BitCodeAbbrevOp(0)); // hasTypeConstraint
2462   // Decl
2463   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2464                            7)); // Packed DeclBits: ModuleOwnershipKind,
2465                                 // isReferenced, isUsed, AccessSpecifier. Other
2466                                 // higher bits should be 0: isImplicit,
2467                                 // HasStandaloneLexicalDC, HasAttrs,
2468                                 // TopLevelDeclInObjCContainer, isInvalidDecl
2469   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
2470   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SubmoduleID
2471   // NamedDecl
2472   Abv->Add(BitCodeAbbrevOp(0));                       // NameKind = Identifier
2473   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Name
2474   Abv->Add(BitCodeAbbrevOp(0));
2475   // TypeDecl
2476   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2477   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type Ref
2478   // TemplateTypeParmDecl
2479   Abv->Add(
2480       BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // wasDeclaredWithTypename
2481   Abv->Add(BitCodeAbbrevOp(0));                    // OwnsDefaultArg
2482   DeclTemplateTypeParmAbbrev = Stream.EmitAbbrev(std::move(Abv));
2483 
2484   // Abbreviation for DECL_USING_SHADOW
2485   Abv = std::make_shared<BitCodeAbbrev>();
2486   Abv->Add(BitCodeAbbrevOp(serialization::DECL_USING_SHADOW));
2487   // Redeclarable
2488   Abv->Add(BitCodeAbbrevOp(0)); // No redeclaration
2489   // Decl
2490   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
2491                            12)); // Packed DeclBits: HasStandaloneLexicalDC,
2492                                  // isInvalidDecl, HasAttrs, isImplicit, isUsed,
2493                                  // isReferenced, TopLevelDeclInObjCContainer,
2494                                  // AccessSpecifier, ModuleOwnershipKind
2495   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
2496   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // SubmoduleID
2497   // NamedDecl
2498   Abv->Add(BitCodeAbbrevOp(0));                       // NameKind = Identifier
2499   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Name
2500   Abv->Add(BitCodeAbbrevOp(0));
2501   // UsingShadowDecl
2502   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));    // TargetDecl
2503   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 11)); // IDNS
2504   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));    // UsingOrNextShadow
2505   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR,
2506                            6)); // InstantiatedFromUsingShadowDecl
2507   DeclUsingShadowAbbrev = Stream.EmitAbbrev(std::move(Abv));
2508 
2509   // Abbreviation for EXPR_DECL_REF
2510   Abv = std::make_shared<BitCodeAbbrev>();
2511   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_DECL_REF));
2512   // Stmt
2513   //  Expr
2514   //  PackingBits: DependenceKind, ValueKind. ObjectKind should be 0.
2515   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
2516   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2517   // DeclRefExpr
2518   // Packing Bits: , HadMultipleCandidates, RefersToEnclosingVariableOrCapture,
2519   // IsImmediateEscalating, NonOdrUseReason.
2520   // GetDeclFound, HasQualifier and ExplicitTemplateArgs should be 0.
2521   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 5));
2522   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclRef
2523   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Location
2524   DeclRefExprAbbrev = Stream.EmitAbbrev(std::move(Abv));
2525 
2526   // Abbreviation for EXPR_INTEGER_LITERAL
2527   Abv = std::make_shared<BitCodeAbbrev>();
2528   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_INTEGER_LITERAL));
2529   //Stmt
2530   // Expr
2531   // DependenceKind, ValueKind, ObjectKind
2532   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 10));
2533   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2534   // Integer Literal
2535   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Location
2536   Abv->Add(BitCodeAbbrevOp(32));                      // Bit Width
2537   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Value
2538   IntegerLiteralAbbrev = Stream.EmitAbbrev(std::move(Abv));
2539 
2540   // Abbreviation for EXPR_CHARACTER_LITERAL
2541   Abv = std::make_shared<BitCodeAbbrev>();
2542   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_CHARACTER_LITERAL));
2543   //Stmt
2544   // Expr
2545   // DependenceKind, ValueKind, ObjectKind
2546   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 10));
2547   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2548   // Character Literal
2549   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // getValue
2550   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Location
2551   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); // getKind
2552   CharacterLiteralAbbrev = Stream.EmitAbbrev(std::move(Abv));
2553 
2554   // Abbreviation for EXPR_IMPLICIT_CAST
2555   Abv = std::make_shared<BitCodeAbbrev>();
2556   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_IMPLICIT_CAST));
2557   // Stmt
2558   // Expr
2559   // Packing Bits: DependenceKind, ValueKind, ObjectKind,
2560   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 10));
2561   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2562   // CastExpr
2563   Abv->Add(BitCodeAbbrevOp(0)); // PathSize
2564   // Packing Bits: CastKind, StoredFPFeatures, isPartOfExplicitCast
2565   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 9));
2566   // ImplicitCastExpr
2567   ExprImplicitCastAbbrev = Stream.EmitAbbrev(std::move(Abv));
2568 
2569   // Abbreviation for EXPR_BINARY_OPERATOR
2570   Abv = std::make_shared<BitCodeAbbrev>();
2571   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_BINARY_OPERATOR));
2572   // Stmt
2573   // Expr
2574   // Packing Bits: DependenceKind. ValueKind and ObjectKind should
2575   // be 0 in this case.
2576   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 5));
2577   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2578   // BinaryOperator
2579   Abv->Add(
2580       BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // OpCode and HasFPFeatures
2581   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2582   BinaryOperatorAbbrev = Stream.EmitAbbrev(std::move(Abv));
2583 
2584   // Abbreviation for EXPR_COMPOUND_ASSIGN_OPERATOR
2585   Abv = std::make_shared<BitCodeAbbrev>();
2586   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_COMPOUND_ASSIGN_OPERATOR));
2587   // Stmt
2588   // Expr
2589   // Packing Bits: DependenceKind. ValueKind and ObjectKind should
2590   // be 0 in this case.
2591   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 5));
2592   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2593   // BinaryOperator
2594   // Packing Bits: OpCode. The HasFPFeatures bit should be 0
2595   Abv->Add(
2596       BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // OpCode and HasFPFeatures
2597   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2598   // CompoundAssignOperator
2599   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHSType
2600   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Result Type
2601   CompoundAssignOperatorAbbrev = Stream.EmitAbbrev(std::move(Abv));
2602 
2603   // Abbreviation for EXPR_CALL
2604   Abv = std::make_shared<BitCodeAbbrev>();
2605   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_CALL));
2606   // Stmt
2607   // Expr
2608   // Packing Bits: DependenceKind, ValueKind, ObjectKind,
2609   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 10));
2610   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2611   // CallExpr
2612   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // NumArgs
2613   Abv->Add(BitCodeAbbrevOp(0));                       // ADLCallKind
2614   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2615   CallExprAbbrev = Stream.EmitAbbrev(std::move(Abv));
2616 
2617   // Abbreviation for EXPR_CXX_OPERATOR_CALL
2618   Abv = std::make_shared<BitCodeAbbrev>();
2619   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_CXX_OPERATOR_CALL));
2620   // Stmt
2621   // Expr
2622   // Packing Bits: DependenceKind, ValueKind, ObjectKind,
2623   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 10));
2624   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2625   // CallExpr
2626   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // NumArgs
2627   Abv->Add(BitCodeAbbrevOp(0));                       // ADLCallKind
2628   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2629   // CXXOperatorCallExpr
2630   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Operator Kind
2631   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2632   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2633   CXXOperatorCallExprAbbrev = Stream.EmitAbbrev(std::move(Abv));
2634 
2635   // Abbreviation for EXPR_CXX_MEMBER_CALL
2636   Abv = std::make_shared<BitCodeAbbrev>();
2637   Abv->Add(BitCodeAbbrevOp(serialization::EXPR_CXX_MEMBER_CALL));
2638   // Stmt
2639   // Expr
2640   // Packing Bits: DependenceKind, ValueKind, ObjectKind,
2641   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 10));
2642   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
2643   // CallExpr
2644   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // NumArgs
2645   Abv->Add(BitCodeAbbrevOp(0));                       // ADLCallKind
2646   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2647   // CXXMemberCallExpr
2648   CXXMemberCallExprAbbrev = Stream.EmitAbbrev(std::move(Abv));
2649 
2650   // Abbreviation for STMT_COMPOUND
2651   Abv = std::make_shared<BitCodeAbbrev>();
2652   Abv->Add(BitCodeAbbrevOp(serialization::STMT_COMPOUND));
2653   // Stmt
2654   // CompoundStmt
2655   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Num Stmts
2656   Abv->Add(BitCodeAbbrevOp(0));                       // hasStoredFPFeatures
2657   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2658   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Source Location
2659   CompoundStmtAbbrev = Stream.EmitAbbrev(std::move(Abv));
2660 
2661   Abv = std::make_shared<BitCodeAbbrev>();
2662   Abv->Add(BitCodeAbbrevOp(serialization::DECL_CONTEXT_LEXICAL));
2663   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob));
2664   DeclContextLexicalAbbrev = Stream.EmitAbbrev(std::move(Abv));
2665 
2666   Abv = std::make_shared<BitCodeAbbrev>();
2667   Abv->Add(BitCodeAbbrevOp(serialization::DECL_CONTEXT_VISIBLE));
2668   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob));
2669   DeclContextVisibleLookupAbbrev = Stream.EmitAbbrev(std::move(Abv));
2670 }
2671 
2672 /// isRequiredDecl - Check if this is a "required" Decl, which must be seen by
2673 /// consumers of the AST.
2674 ///
2675 /// Such decls will always be deserialized from the AST file, so we would like
2676 /// this to be as restrictive as possible. Currently the predicate is driven by
2677 /// code generation requirements, if other clients have a different notion of
2678 /// what is "required" then we may have to consider an alternate scheme where
2679 /// clients can iterate over the top-level decls and get information on them,
2680 /// without necessary deserializing them. We could explicitly require such
2681 /// clients to use a separate API call to "realize" the decl. This should be
2682 /// relatively painless since they would presumably only do it for top-level
2683 /// decls.
2684 static bool isRequiredDecl(const Decl *D, ASTContext &Context,
2685                            Module *WritingModule) {
2686   // Named modules have different semantics than header modules. Every named
2687   // module units owns a translation unit. So the importer of named modules
2688   // doesn't need to deserilize everything ahead of time.
2689   if (WritingModule && WritingModule->isNamedModule()) {
2690     // The PragmaCommentDecl and PragmaDetectMismatchDecl are MSVC's extension.
2691     // And the behavior of MSVC for such cases will leak this to the module
2692     // users. Given pragma is not a standard thing, the compiler has the space
2693     // to do their own decision. Let's follow MSVC here.
2694     if (isa<PragmaCommentDecl, PragmaDetectMismatchDecl>(D))
2695       return true;
2696     return false;
2697   }
2698 
2699   // An ObjCMethodDecl is never considered as "required" because its
2700   // implementation container always is.
2701 
2702   // File scoped assembly or obj-c or OMP declare target implementation must be
2703   // seen.
2704   if (isa<FileScopeAsmDecl, TopLevelStmtDecl, ObjCImplDecl>(D))
2705     return true;
2706 
2707   if (WritingModule && isPartOfPerModuleInitializer(D)) {
2708     // These declarations are part of the module initializer, and are emitted
2709     // if and when the module is imported, rather than being emitted eagerly.
2710     return false;
2711   }
2712 
2713   return Context.DeclMustBeEmitted(D);
2714 }
2715 
2716 void ASTWriter::WriteDecl(ASTContext &Context, Decl *D) {
2717   PrettyDeclStackTraceEntry CrashInfo(Context, D, SourceLocation(),
2718                                       "serializing");
2719 
2720   // Determine the ID for this declaration.
2721   serialization::DeclID ID;
2722   assert(!D->isFromASTFile() && "should not be emitting imported decl");
2723   serialization::DeclID &IDR = DeclIDs[D];
2724   if (IDR == 0)
2725     IDR = NextDeclID++;
2726 
2727   ID = IDR;
2728 
2729   assert(ID >= FirstDeclID && "invalid decl ID");
2730 
2731   RecordData Record;
2732   ASTDeclWriter W(*this, Context, Record);
2733 
2734   // Build a record for this declaration
2735   W.Visit(D);
2736 
2737   // Emit this declaration to the bitstream.
2738   uint64_t Offset = W.Emit(D);
2739 
2740   // Record the offset for this declaration
2741   SourceLocation Loc = D->getLocation();
2742   unsigned Index = ID - FirstDeclID;
2743   if (DeclOffsets.size() == Index)
2744     DeclOffsets.emplace_back(getAdjustedLocation(Loc), Offset,
2745                              DeclTypesBlockStartOffset);
2746   else if (DeclOffsets.size() < Index) {
2747     // FIXME: Can/should this happen?
2748     DeclOffsets.resize(Index+1);
2749     DeclOffsets[Index].setLocation(getAdjustedLocation(Loc));
2750     DeclOffsets[Index].setBitOffset(Offset, DeclTypesBlockStartOffset);
2751   } else {
2752     llvm_unreachable("declarations should be emitted in ID order");
2753   }
2754 
2755   SourceManager &SM = Context.getSourceManager();
2756   if (Loc.isValid() && SM.isLocalSourceLocation(Loc))
2757     associateDeclWithFile(D, ID);
2758 
2759   // Note declarations that should be deserialized eagerly so that we can add
2760   // them to a record in the AST file later.
2761   if (isRequiredDecl(D, Context, WritingModule))
2762     EagerlyDeserializedDecls.push_back(ID);
2763 }
2764 
2765 void ASTRecordWriter::AddFunctionDefinition(const FunctionDecl *FD) {
2766   // Switch case IDs are per function body.
2767   Writer->ClearSwitchCaseIDs();
2768 
2769   assert(FD->doesThisDeclarationHaveABody());
2770   bool ModulesCodegen = false;
2771   if (!FD->isDependentContext()) {
2772     std::optional<GVALinkage> Linkage;
2773     if (Writer->WritingModule &&
2774         Writer->WritingModule->isInterfaceOrPartition()) {
2775       // When building a C++20 module interface unit or a partition unit, a
2776       // strong definition in the module interface is provided by the
2777       // compilation of that unit, not by its users. (Inline functions are still
2778       // emitted in module users.)
2779       Linkage = Writer->Context->GetGVALinkageForFunction(FD);
2780       ModulesCodegen = *Linkage >= GVA_StrongExternal;
2781     }
2782     if (Writer->Context->getLangOpts().ModulesCodegen ||
2783         (FD->hasAttr<DLLExportAttr>() &&
2784          Writer->Context->getLangOpts().BuildingPCHWithObjectFile)) {
2785 
2786       // Under -fmodules-codegen, codegen is performed for all non-internal,
2787       // non-always_inline functions, unless they are available elsewhere.
2788       if (!FD->hasAttr<AlwaysInlineAttr>()) {
2789         if (!Linkage)
2790           Linkage = Writer->Context->GetGVALinkageForFunction(FD);
2791         ModulesCodegen =
2792             *Linkage != GVA_Internal && *Linkage != GVA_AvailableExternally;
2793       }
2794     }
2795   }
2796   Record->push_back(ModulesCodegen);
2797   if (ModulesCodegen)
2798     Writer->ModularCodegenDecls.push_back(Writer->GetDeclRef(FD));
2799   if (auto *CD = dyn_cast<CXXConstructorDecl>(FD)) {
2800     Record->push_back(CD->getNumCtorInitializers());
2801     if (CD->getNumCtorInitializers())
2802       AddCXXCtorInitializers(llvm::ArrayRef(CD->init_begin(), CD->init_end()));
2803   }
2804   AddStmt(FD->getBody());
2805 }
2806