Allow deserialization of just the fields of a record, when we want to iterate over them,

instead of deserializing the complete declaration context of the record.

Iterating over the fields of a record is very common (e.g to determine the layout), unfortunately we needlessly deserialize every declaration
that the declaration context of the record contains; this can be bad for large C++ classes that contain a lot of methods.
Fix this by allow deserialization of just the fields when we want to iterate over them.
Progress for rdar://7260160.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@116507 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 18 insertions, 13 deletions

diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index 9ee818367b..23f2eaac66 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -903,8 +903,8 @@ bool ASTReader::ReadDeclContextStorage(llvm::BitstreamCursor &Cursor,
       return true;
     }
 
-    Info.LexicalDecls = reinterpret_cast<const DeclID*>(Blob);
-    Info.NumLexicalDecls = BlobLen / sizeof(DeclID);
+    Info.LexicalDecls = reinterpret_cast<const KindDeclIDPair*>(Blob);
+    Info.NumLexicalDecls = BlobLen / sizeof(KindDeclIDPair);
   } else {
     Info.LexicalDecls = 0;
     Info.NumLexicalDecls = 0;
@@ -1778,8 +1778,8 @@ ASTReader::ReadASTBlock(PerFileData &F) {
     case TU_UPDATE_LEXICAL: {
       DeclContextInfo Info = {
         /* No visible information */ 0,
-        reinterpret_cast<const DeclID *>(BlobStart),
-        BlobLen / sizeof(DeclID)
+        reinterpret_cast<const KindDeclIDPair *>(BlobStart),
+        BlobLen / sizeof(KindDeclIDPair)
       };
       DeclContextOffsets[Context ? Context->getTranslationUnitDecl() : 0]
         .push_back(Info);
@@ -3242,6 +3242,7 @@ Stmt *ASTReader::GetExternalDeclStmt(uint64_t Offset) {
 }
 
 bool ASTReader::FindExternalLexicalDecls(const DeclContext *DC,
+                                         bool (*isKindWeWant)(Decl::Kind),
                                          llvm::SmallVectorImpl<Decl*> &Decls) {
   assert(DC->hasExternalLexicalStorage() &&
          "DeclContext has no lexical decls in storage");
@@ -3258,9 +3259,12 @@ bool ASTReader::FindExternalLexicalDecls(const DeclContext *DC,
       continue;
 
     // Load all of the declaration IDs
-    for (const DeclID *ID = I->LexicalDecls, *IDE = ID + I->NumLexicalDecls;
-         ID != IDE; ++ID) {
-      Decl *D = GetDecl(*ID);
+    for (const KindDeclIDPair *ID = I->LexicalDecls,
+                              *IDE = ID + I->NumLexicalDecls; ID != IDE; ++ID) {
+      if (isKindWeWant && !isKindWeWant((Decl::Kind)ID->first))
+        continue;
+
+      Decl *D = GetDecl(ID->second);
       assert(D && "Null decl in lexical decls");
       Decls.push_back(D);
     }
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index eae47db44e..8dffe1a950 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -1474,14 +1474,15 @@ uint64_t ASTWriter::WriteDeclContextLexicalBlock(ASTContext &Context,
   uint64_t Offset = Stream.GetCurrentBitNo();
   RecordData Record;
   Record.push_back(DECL_CONTEXT_LEXICAL);
-  llvm::SmallVector<DeclID, 64> Decls;
+  llvm::SmallVector<KindDeclIDPair, 64> Decls;
   for (DeclContext::decl_iterator D = DC->decls_begin(), DEnd = DC->decls_end();
          D != DEnd; ++D)
-    Decls.push_back(GetDeclRef(*D));
+    Decls.push_back(std::make_pair((*D)->getKind(), GetDeclRef(*D)));
 
   ++NumLexicalDeclContexts;
   Stream.EmitRecordWithBlob(DeclContextLexicalAbbrev, Record,
-     reinterpret_cast<char*>(Decls.data()), Decls.size() * sizeof(DeclID));
+                            reinterpret_cast<char*>(Decls.data()),
+                            Decls.size() * sizeof(KindDeclIDPair));
   return Offset;
 }
 
@@ -2471,12 +2472,12 @@ void ASTWriter::WriteASTChain(Sema &SemaRef, MemorizeStatCalls *StatCalls,
   // We don't start with the translation unit, but with its decls that
   // don't come from the chained PCH.
   const TranslationUnitDecl *TU = Context.getTranslationUnitDecl();
-  llvm::SmallVector<DeclID, 64> NewGlobalDecls;
+  llvm::SmallVector<KindDeclIDPair, 64> NewGlobalDecls;
   for (DeclContext::decl_iterator I = TU->noload_decls_begin(),
                                   E = TU->noload_decls_end();
        I != E; ++I) {
     if ((*I)->getPCHLevel() == 0)
-      NewGlobalDecls.push_back(GetDeclRef(*I));
+      NewGlobalDecls.push_back(std::make_pair((*I)->getKind(), GetDeclRef(*I)));
     else if ((*I)->isChangedSinceDeserialization())
       (void)GetDeclRef(*I); // Make sure it's written, but don't record it.
   }
@@ -2489,7 +2490,7 @@ void ASTWriter::WriteASTChain(Sema &SemaRef, MemorizeStatCalls *StatCalls,
   Record.push_back(TU_UPDATE_LEXICAL);
   Stream.EmitRecordWithBlob(TuUpdateLexicalAbbrev, Record,
                           reinterpret_cast<const char*>(NewGlobalDecls.data()),
-                          NewGlobalDecls.size() * sizeof(DeclID));
+                          NewGlobalDecls.size() * sizeof(KindDeclIDPair));
   // And in C++, a visible updates block for the TU.
   if (Context.getLangOptions().CPlusPlus) {
     Abv = new llvm::BitCodeAbbrev();