Apart from storing/retrieving the previous redeclaration from PCH, also store/retrieve the most recent

redeclaration. That way we are sure that the full redeclarations chain is loaded.

When using chained PCHs, first declarations point to the most recent redeclarations in the same PCH.
To address this use a REDECLS_UPDATE_LATEST record block to keep track of which first declarations need
to point to a most recent redeclaration in another PCH.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@110125 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 144 insertions, 18 deletions

diff --git a/lib/Frontend/PCHReader.cpp b/lib/Frontend/PCHReader.cpp
index b415f8dea5..35909a0555 100644
--- a/lib/Frontend/PCHReader.cpp
+++ b/lib/Frontend/PCHReader.cpp
@@ -1557,6 +1557,18 @@ PCHReader::ReadPCHBlock(PerFileData &F) {
       break;
     }
 
+    case pch::REDECLS_UPDATE_LATEST: {
+      assert(Record.size() % 2 == 0 && "Expected pairs of DeclIDs");
+      for (unsigned i = 0, e = Record.size(); i < e; i += 2) {
+        pch::DeclID First = Record[i], Latest = Record[i+1];
+        assert((FirstLatestDeclIDs.find(First) == FirstLatestDeclIDs.end() ||
+                Latest > FirstLatestDeclIDs[First]) &&
+               "The new latest is supposed to come after the previous latest");
+        FirstLatestDeclIDs[First] = Latest;
+      }
+      break;
+    }
+
     case pch::LANGUAGE_OPTIONS:
       if (ParseLanguageOptions(Record) && !DisableValidation)
         return IgnorePCH;
@@ -2868,7 +2880,7 @@ Decl *PCHReader::GetExternalDecl(uint32_t ID) {
 
 TranslationUnitDecl *PCHReader::GetTranslationUnitDecl() {
   if (!DeclsLoaded[0]) {
-    ReadDeclRecord(0);
+    ReadDeclRecord(0, 0);
     if (DeserializationListener)
       DeserializationListener->DeclRead(1, DeclsLoaded[0]);
   }
@@ -2887,7 +2899,7 @@ Decl *PCHReader::GetDecl(pch::DeclID ID) {
 
   unsigned Index = ID - 1;
   if (!DeclsLoaded[Index]) {
-    ReadDeclRecord(Index);
+    ReadDeclRecord(Index, ID);
     if (DeserializationListener)
       DeserializationListener->DeclRead(ID, DeclsLoaded[Index]);
   }
diff --git a/lib/Frontend/PCHReaderDecl.cpp b/lib/Frontend/PCHReaderDecl.cpp
index e9428cc0b4..21beb42e93 100644
--- a/lib/Frontend/PCHReaderDecl.cpp
+++ b/lib/Frontend/PCHReaderDecl.cpp
@@ -31,6 +31,7 @@ namespace clang {
   class PCHDeclReader : public DeclVisitor<PCHDeclReader, void> {
     PCHReader &Reader;
     llvm::BitstreamCursor &Cursor;
+    const pch::DeclID ThisDeclID;
     const PCHReader::RecordData &Record;
     unsigned &Idx;
     pch::TypeID TypeIDForTypeDecl;
@@ -39,9 +40,10 @@ namespace clang {
 
   public:
     PCHDeclReader(PCHReader &Reader, llvm::BitstreamCursor &Cursor,
-                  const PCHReader::RecordData &Record, unsigned &Idx)
-      : Reader(Reader), Cursor(Cursor), Record(Record), Idx(Idx),
-        TypeIDForTypeDecl(0) { }
+                  pch::DeclID thisDeclID, const PCHReader::RecordData &Record,
+                  unsigned &Idx)
+      : Reader(Reader), Cursor(Cursor), ThisDeclID(thisDeclID), Record(Record),
+        Idx(Idx), TypeIDForTypeDecl(0) { }
 
     void Visit(Decl *D);
 
@@ -93,6 +95,7 @@ namespace clang {
     void VisitBlockDecl(BlockDecl *BD);
 
     std::pair<uint64_t, uint64_t> VisitDeclContext(DeclContext *DC);
+    template <typename T> void VisitRedeclarable(Redeclarable<T> *D);
 
     // FIXME: Reorder according to DeclNodes.td?
     void VisitObjCMethodDecl(ObjCMethodDecl *D);
@@ -178,8 +181,7 @@ void PCHDeclReader::VisitTypedefDecl(TypedefDecl *TD) {
 void PCHDeclReader::VisitTagDecl(TagDecl *TD) {
   VisitTypeDecl(TD);
   TD->IdentifierNamespace = Record[Idx++];
-  TD->setPreviousDeclaration(
-                        cast_or_null<TagDecl>(Reader.GetDecl(Record[Idx++])));
+  VisitRedeclarable(TD);
   TD->setTagKind((TagDecl::TagKind)Record[Idx++]);
   TD->setDefinition(Record[Idx++]);
   TD->setEmbeddedInDeclarator(Record[Idx++]);
@@ -305,10 +307,7 @@ void PCHDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
   // FunctionDecl's body is handled last at PCHReaderDecl::Visit,
   // after everything else is read.
 
-  // Avoid side effects and invariant checking of FunctionDecl's
-  // setPreviousDeclaration.
-  FD->redeclarable_base::setPreviousDeclaration(
-                   cast_or_null<FunctionDecl>(Reader.GetDecl(Record[Idx++])));
+  VisitRedeclarable(FD);
   FD->setStorageClass((FunctionDecl::StorageClass)Record[Idx++]);
   FD->setStorageClassAsWritten((FunctionDecl::StorageClass)Record[Idx++]);
   FD->setInlineSpecified(Record[Idx++]);
@@ -550,8 +549,7 @@ void PCHDeclReader::VisitVarDecl(VarDecl *VD) {
   VD->setDeclaredInCondition(Record[Idx++]);
   VD->setExceptionVariable(Record[Idx++]);
   VD->setNRVOVariable(Record[Idx++]);
-  VD->setPreviousDeclaration(
-                         cast_or_null<VarDecl>(Reader.GetDecl(Record[Idx++])));
+  VisitRedeclarable(VD);
   if (Record[Idx++])
     VD->setInit(Reader.ReadExpr(Cursor));
 
@@ -918,6 +916,25 @@ void PCHDeclReader::VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D) {
 
     RedeclarableTemplateDecl *LatestDecl = 
         cast_or_null<RedeclarableTemplateDecl>(Reader.GetDecl(Record[Idx++]));
+  
+    // This decl is a first one and the latest declaration that it points to is
+    // in the same PCH. However, if this actually needs to point to a
+    // redeclaration in another chained PCH, we need to update it by checking
+    // the FirstLatestDeclIDs map which tracks this kind of decls.
+    assert(Reader.GetDecl(ThisDeclID) == D && "Invalid ThisDeclID ?");
+    PCHReader::FirstLatestDeclIDMap::iterator I
+        = Reader.FirstLatestDeclIDs.find(ThisDeclID);
+    if (I != Reader.FirstLatestDeclIDs.end()) {
+      Decl *NewLatest = Reader.GetDecl(I->second);
+      assert((LatestDecl->getLocation().isInvalid() ||
+              NewLatest->getLocation().isInvalid()  ||
+              Reader.SourceMgr.isBeforeInTranslationUnit(
+                                                   LatestDecl->getLocation(),
+                                                   NewLatest->getLocation())) &&
+             "The new latest is supposed to come after the previous latest");
+      LatestDecl = cast<RedeclarableTemplateDecl>(NewLatest);
+    }
+
     assert(LatestDecl->getKind() == D->getKind() && "Latest kind mismatch");
     D->getCommonPtr()->Latest = LatestDecl;
   }
@@ -1072,6 +1089,54 @@ PCHDeclReader::VisitDeclContext(DeclContext *DC) {
   return std::make_pair(LexicalOffset, VisibleOffset);
 }
 
+template <typename T>
+void PCHDeclReader::VisitRedeclarable(Redeclarable<T> *D) {
+  enum RedeclKind { NoRedeclaration = 0, PointsToPrevious, PointsToLatest };
+  RedeclKind Kind = (RedeclKind)Record[Idx++];
+  switch (Kind) {
+  default:
+    assert(0 && "Out of sync with PCHDeclWriter::VisitRedeclarable or messed up"
+                " reading");
+  case NoRedeclaration:
+    break;
+  case PointsToPrevious:
+    D->RedeclLink = typename Redeclarable<T>::PreviousDeclLink(
+                                cast_or_null<T>(Reader.GetDecl(Record[Idx++])));
+    break;
+  case PointsToLatest:
+    D->RedeclLink = typename Redeclarable<T>::LatestDeclLink(
+                                cast_or_null<T>(Reader.GetDecl(Record[Idx++])));
+    break;
+  }
+
+  assert(!(Kind == PointsToPrevious &&
+           Reader.FirstLatestDeclIDs.find(ThisDeclID) !=
+               Reader.FirstLatestDeclIDs.end()) &&
+         "This decl is not first, it should not be in the map");
+  if (Kind == PointsToPrevious)
+    return;
+
+  // This decl is a first one and the latest declaration that it points to is in
+  // the same PCH. However, if this actually needs to point to a redeclaration
+  // in another chained PCH, we need to update it by checking the
+  // FirstLatestDeclIDs map which tracks this kind of decls.
+  assert(Reader.GetDecl(ThisDeclID) == static_cast<T*>(D) &&
+         "Invalid ThisDeclID ?");
+  PCHReader::FirstLatestDeclIDMap::iterator I
+      = Reader.FirstLatestDeclIDs.find(ThisDeclID);
+  if (I != Reader.FirstLatestDeclIDs.end()) {
+    Decl *NewLatest = Reader.GetDecl(I->second);
+    assert((D->getMostRecentDeclaration()->getLocation().isInvalid() ||
+            NewLatest->getLocation().isInvalid() ||
+            Reader.SourceMgr.isBeforeInTranslationUnit(
+                                   D->getMostRecentDeclaration()->getLocation(),
+                                   NewLatest->getLocation())) &&
+           "The new latest is supposed to come after the previous latest");
+    D->RedeclLink
+        = typename Redeclarable<T>::LatestDeclLink(cast_or_null<T>(NewLatest));
+  }
+}
+
 //===----------------------------------------------------------------------===//
 // Attribute Reading
 //===----------------------------------------------------------------------===//
@@ -1304,7 +1369,7 @@ PCHReader::RecordLocation PCHReader::DeclCursorForIndex(unsigned Index) {
 }
 
 /// \brief Read the declaration at the given offset from the PCH file.
-Decl *PCHReader::ReadDeclRecord(unsigned Index) {
+Decl *PCHReader::ReadDeclRecord(unsigned Index, pch::DeclID ID) {
   RecordLocation Loc = DeclCursorForIndex(Index);
   llvm::BitstreamCursor &DeclsCursor = *Loc.first;
   // Keep track of where we are in the stream, then jump back there
@@ -1320,7 +1385,7 @@ Decl *PCHReader::ReadDeclRecord(unsigned Index) {
   RecordData Record;
   unsigned Code = DeclsCursor.ReadCode();
   unsigned Idx = 0;
-  PCHDeclReader Reader(*this, DeclsCursor, Record, Idx);
+  PCHDeclReader Reader(*this, DeclsCursor, ID, Record, Idx);
 
   Decl *D = 0;
   switch ((pch::DeclCode)DeclsCursor.ReadRecord(Code, Record)) {
diff --git a/lib/Frontend/PCHWriter.cpp b/lib/Frontend/PCHWriter.cpp
index 75592a41c8..776a40940d 100644
--- a/lib/Frontend/PCHWriter.cpp
+++ b/lib/Frontend/PCHWriter.cpp
@@ -2410,6 +2410,19 @@ void PCHWriter::WritePCHChain(Sema &SemaRef, MemorizeStatCalls *StatCalls,
   WriteIdentifierTable(PP);
   WriteTypeDeclOffsets();
 
+  /// Build a record containing first declarations from a chained PCH and the
+  /// most recent declarations in this PCH that they point to.
+  RecordData FirstLatestDeclIDs;
+  for (FirstLatestDeclMap::iterator
+        I = FirstLatestDecls.begin(), E = FirstLatestDecls.end(); I != E; ++I) {
+    assert(I->first->getPCHLevel() > I->second->getPCHLevel() &&
+           "Expected first & second to be in different PCHs");
+    AddDeclRef(I->first, FirstLatestDeclIDs);
+    AddDeclRef(I->second, FirstLatestDeclIDs);
+  }
+  if (!FirstLatestDeclIDs.empty())
+    Stream.EmitRecord(pch::REDECLS_UPDATE_LATEST, FirstLatestDeclIDs);
+
   // Write the record containing external, unnamed definitions.
   if (!ExternalDefinitions.empty())
     Stream.EmitRecord(pch::EXTERNAL_DEFINITIONS, ExternalDefinitions);
diff --git a/lib/Frontend/PCHWriterDecl.cpp b/lib/Frontend/PCHWriterDecl.cpp
index 28a82cd23f..9e9835adb4 100644
--- a/lib/Frontend/PCHWriterDecl.cpp
+++ b/lib/Frontend/PCHWriterDecl.cpp
@@ -92,6 +92,7 @@ namespace clang {
 
     void VisitDeclContext(DeclContext *DC, uint64_t LexicalOffset,
                           uint64_t VisibleOffset);
+    template <typename T> void VisitRedeclarable(Redeclarable<T> *D);
 
 
     // FIXME: Put in the same order is DeclNodes.td?
@@ -163,7 +164,7 @@ void PCHDeclWriter::VisitTypedefDecl(TypedefDecl *D) {
 void PCHDeclWriter::VisitTagDecl(TagDecl *D) {
   VisitTypeDecl(D);
   Record.push_back(D->getIdentifierNamespace());
-  Writer.AddDeclRef(D->getPreviousDeclaration(), Record);
+  VisitRedeclarable(D);
   Record.push_back((unsigned)D->getTagKind()); // FIXME: stable encoding
   Record.push_back(D->isDefinition());
   Record.push_back(D->isEmbeddedInDeclarator());
@@ -279,7 +280,7 @@ void PCHDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
   // FunctionDecl's body is handled last at PCHWriterDecl::Visit,
   // after everything else is written.
 
-  Writer.AddDeclRef(D->getPreviousDeclaration(), Record);
+  VisitRedeclarable(D);
   Record.push_back(D->getStorageClass()); // FIXME: stable encoding
   Record.push_back(D->getStorageClassAsWritten());
   Record.push_back(D->isInlineSpecified());
@@ -500,7 +501,7 @@ void PCHDeclWriter::VisitVarDecl(VarDecl *D) {
   Record.push_back(D->isDeclaredInCondition());
   Record.push_back(D->isExceptionVariable());
   Record.push_back(D->isNRVOVariable());
-  Writer.AddDeclRef(D->getPreviousDeclaration(), Record);
+  VisitRedeclarable(D);
   Record.push_back(D->getInit() ? 1 : 0);
   if (D->getInit())
     Writer.AddStmt(D->getInit());
@@ -854,6 +855,18 @@ void PCHDeclWriter::VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D) {
       Record.push_back(D->isMemberSpecialization());
 
     Writer.AddDeclRef(D->getCommonPtr()->Latest, Record);
+  } else {
+    RedeclarableTemplateDecl *First = D->getFirstDeclaration();
+    assert(First != D);
+    // If this is a most recent redeclaration that is pointed to by a first decl
+    // in a chained PCH, keep track of the association with the map so we can
+    // update the first decl during PCH reading.
+    if (First->getMostRecentDeclaration() == D &&
+        First->getPCHLevel() > D->getPCHLevel()) {
+      assert(Writer.FirstLatestDecls.find(First)==Writer.FirstLatestDecls.end()
+             && "The latest is already set");
+      Writer.FirstLatestDecls[First] = D;
+    }
   }
 }
 
@@ -1016,6 +1029,29 @@ void PCHDeclWriter::VisitDeclContext(DeclContext *DC, uint64_t LexicalOffset,
   Record.push_back(VisibleOffset);
 }
 
+template <typename T>
+void PCHDeclWriter::VisitRedeclarable(Redeclarable<T> *D) {
+  enum { NoRedeclaration = 0, PointsToPrevious, PointsToLatest };
+  if (D->RedeclLink.getNext() == D) {
+    Record.push_back(NoRedeclaration);
+  } else {
+    Record.push_back(D->RedeclLink.NextIsPrevious() ? PointsToPrevious
+                                                    : PointsToLatest);
+    Writer.AddDeclRef(D->RedeclLink.getPointer(), Record);
+  }
+
+  T *First = D->getFirstDeclaration();
+  T *ThisDecl = static_cast<T*>(D);
+  // If this is a most recent redeclaration that is pointed to by a first decl
+  // in a chained PCH, keep track of the association with the map so we can
+  // update the first decl during PCH reading.
+  if (ThisDecl != First && First->getMostRecentDeclaration() == ThisDecl &&
+      First->getPCHLevel() > ThisDecl->getPCHLevel()) {
+    assert(Writer.FirstLatestDecls.find(First) == Writer.FirstLatestDecls.end()
+           && "The latest is already set");
+    Writer.FirstLatestDecls[First] = ThisDecl;
+  }
+}
 
 //===----------------------------------------------------------------------===//
 // PCHWriter Implementation