[modules] If the semantic and lexical DC of a decl are the same, write out the

second one as 0 instead of writing the same bits to the module file twice.
This typically reduces PCM file size by about 1%.

llvm-svn: 255384

2 files changed, 32 insertions, 17 deletions

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index e55786ef0c4..2c868cbb9fc 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -476,6 +476,8 @@ void ASTDeclReader::VisitDecl(Decl *D) {
     // placeholder.
     GlobalDeclID SemaDCIDForTemplateParmDecl = ReadDeclID(Record, Idx);
     GlobalDeclID LexicalDCIDForTemplateParmDecl = ReadDeclID(Record, Idx);
+    if (!LexicalDCIDForTemplateParmDecl)
+      LexicalDCIDForTemplateParmDecl = SemaDCIDForTemplateParmDecl;
     Reader.addPendingDeclContextInfo(D,
                                      SemaDCIDForTemplateParmDecl,
                                      LexicalDCIDForTemplateParmDecl);
@@ -483,6 +485,8 @@ void ASTDeclReader::VisitDecl(Decl *D) {
   } else {
     DeclContext *SemaDC = ReadDeclAs<DeclContext>(Record, Idx);
     DeclContext *LexicalDC = ReadDeclAs<DeclContext>(Record, Idx);
+    if (!LexicalDC)
+      LexicalDC = SemaDC;
     DeclContext *MergedSemaDC = Reader.MergedDeclContexts.lookup(SemaDC);
     // Avoid calling setLexicalDeclContext() directly because it uses
     // Decl::getASTContext() internally which is unsafe during derialization.
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index cc67b172bef..20ca6d6fd51 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -276,7 +276,10 @@ void ASTDeclWriter::Visit(Decl *D) {
 
 void ASTDeclWriter::VisitDecl(Decl *D) {
   Writer.AddDeclRef(cast_or_null<Decl>(D->getDeclContext()), Record);
-  Writer.AddDeclRef(cast_or_null<Decl>(D->getLexicalDeclContext()), Record);
+  if (D->getDeclContext() != D->getLexicalDeclContext())
+    Writer.AddDeclRef(cast_or_null<Decl>(D->getLexicalDeclContext()), Record);
+  else
+    Record.push_back(0);
   Record.push_back(D->isInvalidDecl());
   Record.push_back(D->hasAttrs());
   if (D->hasAttrs())
@@ -340,7 +343,8 @@ void ASTDeclWriter::VisitTypedefNameDecl(TypedefNameDecl *D) {
 
 void ASTDeclWriter::VisitTypedefDecl(TypedefDecl *D) {
   VisitTypedefNameDecl(D);
-  if (!D->hasAttrs() &&
+  if (D->getDeclContext() == D->getLexicalDeclContext() &&
+      !D->hasAttrs() &&
       !D->isImplicit() &&
       D->getFirstDecl() == D->getMostRecentDecl() &&
       !D->isInvalidDecl() &&
@@ -402,7 +406,8 @@ void ASTDeclWriter::VisitEnumDecl(EnumDecl *D) {
     Writer.AddDeclRef(nullptr, Record);
   }
 
-  if (!D->hasAttrs() &&
+  if (D->getDeclContext() == D->getLexicalDeclContext() &&
+      !D->hasAttrs() &&
       !D->isImplicit() &&
       !D->isUsed(false) &&
       !D->hasExtInfo() &&
@@ -430,7 +435,8 @@ void ASTDeclWriter::VisitRecordDecl(RecordDecl *D) {
   Record.push_back(D->hasObjectMember());
   Record.push_back(D->hasVolatileMember());
 
-  if (!D->hasAttrs() &&
+  if (D->getDeclContext() == D->getLexicalDeclContext() &&
+      !D->hasAttrs() &&
       !D->isImplicit() &&
       !D->isUsed(false) &&
       !D->hasExtInfo() &&
@@ -688,7 +694,8 @@ void ASTDeclWriter::VisitObjCIvarDecl(ObjCIvarDecl *D) {
   Record.push_back(D->getAccessControl());
   Record.push_back(D->getSynthesize());
 
-  if (!D->hasAttrs() &&
+  if (D->getDeclContext() == D->getLexicalDeclContext() &&
+      !D->hasAttrs() &&
       !D->isImplicit() &&
       !D->isUsed(false) &&
       !D->isInvalidDecl() &&
@@ -820,7 +827,8 @@ void ASTDeclWriter::VisitFieldDecl(FieldDecl *D) {
   if (!D->getDeclName())
     Writer.AddDeclRef(Context.getInstantiatedFromUnnamedFieldDecl(D), Record);
 
-  if (!D->hasAttrs() &&
+  if (D->getDeclContext() == D->getLexicalDeclContext() &&
+      !D->hasAttrs() &&
       !D->isImplicit() &&
       !D->isUsed(false) &&
       !D->isInvalidDecl() &&
@@ -894,7 +902,8 @@ void ASTDeclWriter::VisitVarDecl(VarDecl *D) {
     Record.push_back(VarNotTemplate);
   }
 
-  if (!D->hasAttrs() &&
+  if (D->getDeclContext() == D->getLexicalDeclContext() &&
+      !D->hasAttrs() &&
       !D->isImplicit() &&
       !D->isUsed(false) &&
       !D->isInvalidDecl() &&
@@ -942,7 +951,8 @@ void ASTDeclWriter::VisitParmVarDecl(ParmVarDecl *D) {
   // If the assumptions about the DECL_PARM_VAR abbrev are true, use it.  Here
   // we dynamically check for the properties that we optimize for, but don't
   // know are true of all PARM_VAR_DECLs.
-  if (!D->hasAttrs() &&
+  if (D->getDeclContext() == D->getLexicalDeclContext() &&
+      !D->hasAttrs() &&
       !D->hasExtInfo() &&
       !D->isImplicit() &&
       !D->isUsed(false) &&
@@ -1162,7 +1172,8 @@ void ASTDeclWriter::VisitCXXMethodDecl(CXXMethodDecl *D) {
     Record.push_back(0);
   }
 
-  if (D->getFirstDecl() == D->getMostRecentDecl() &&
+  if (D->getDeclContext() == D->getLexicalDeclContext() &&
+      D->getFirstDecl() == D->getMostRecentDecl() &&
       !D->isInvalidDecl() &&
       !D->hasAttrs() &&
       !D->isTopLevelDeclInObjCContainer() &&
@@ -1631,7 +1642,7 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(serialization::DECL_FIELD));
   // Decl
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LexicalDeclContext
+  Abv->Add(BitCodeAbbrevOp(0));                       // LexicalDeclContext
   Abv->Add(BitCodeAbbrevOp(0));                       // isInvalidDecl
   Abv->Add(BitCodeAbbrevOp(0));                       // HasAttrs
   Abv->Add(BitCodeAbbrevOp(0));                       // isImplicit
@@ -1664,7 +1675,7 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(serialization::DECL_OBJC_IVAR));
   // Decl
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LexicalDeclContext
+  Abv->Add(BitCodeAbbrevOp(0));                       // LexicalDeclContext
   Abv->Add(BitCodeAbbrevOp(0));                       // isInvalidDecl
   Abv->Add(BitCodeAbbrevOp(0));                       // HasAttrs
   Abv->Add(BitCodeAbbrevOp(0));                       // isImplicit
@@ -1702,7 +1713,7 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(0));                       // No redeclaration
   // Decl
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LexicalDeclContext
+  Abv->Add(BitCodeAbbrevOp(0));                       // LexicalDeclContext
   Abv->Add(BitCodeAbbrevOp(0));                       // isInvalidDecl
   Abv->Add(BitCodeAbbrevOp(0));                       // HasAttrs
   Abv->Add(BitCodeAbbrevOp(0));                       // isImplicit
@@ -1750,7 +1761,7 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(0));                       // No redeclaration
   // Decl
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LexicalDeclContext
+  Abv->Add(BitCodeAbbrevOp(0));                       // LexicalDeclContext
   Abv->Add(BitCodeAbbrevOp(0));                       // isInvalidDecl
   Abv->Add(BitCodeAbbrevOp(0));                       // HasAttrs
   Abv->Add(BitCodeAbbrevOp(0));                       // isImplicit
@@ -1793,7 +1804,7 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(0));                       // No redeclaration
   // Decl
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LexicalDeclContext
+  Abv->Add(BitCodeAbbrevOp(0));                       // LexicalDeclContext
   Abv->Add(BitCodeAbbrevOp(0));                       // isInvalidDecl
   Abv->Add(BitCodeAbbrevOp(0));                       // HasAttrs
   Abv->Add(BitCodeAbbrevOp(0));                       // isImplicit
@@ -1840,7 +1851,7 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(0));                       // No redeclaration
   // Decl
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LexicalDeclContext
+  Abv->Add(BitCodeAbbrevOp(0));                       // LexicalDeclContext
   Abv->Add(BitCodeAbbrevOp(0));                       // isInvalidDecl
   Abv->Add(BitCodeAbbrevOp(0));                       // HasAttrs
   Abv->Add(BitCodeAbbrevOp(0));                       // isImplicit
@@ -1869,7 +1880,7 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(0));                       // No redeclaration
   // Decl
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclContext
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LexicalDeclContext
+  Abv->Add(BitCodeAbbrevOp(0));                       // LexicalDeclContext
   Abv->Add(BitCodeAbbrevOp(0));                       // isInvalidDecl
   Abv->Add(BitCodeAbbrevOp(0));                       // HasAttrs
   Abv->Add(BitCodeAbbrevOp(0));                       // isImplicit
@@ -1915,7 +1926,7 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(0));                         // CanonicalDecl
   // Decl
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // DeclContext
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // LexicalDeclContext
+  Abv->Add(BitCodeAbbrevOp(0));                         // LexicalDeclContext
   Abv->Add(BitCodeAbbrevOp(0));                         // Invalid
   Abv->Add(BitCodeAbbrevOp(0));                         // HasAttrs
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Implicit