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