1 files changed, 29 insertions, 71 deletions

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 375bdfb392e..5aeb3d1e517 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -123,9 +123,6 @@ namespace clang {
     /// \brief RAII class used to capture the first ID within a redeclaration
     /// chain and to introduce it into the list of pending redeclaration chains
     /// on destruction.
-    ///
-    /// The caller can choose not to introduce this ID into the list of pending
-    /// redeclaration chains by calling \c suppress().
     class RedeclarableResult {
       ASTReader &Reader;
       GlobalDeclID FirstID;
@@ -149,9 +146,11 @@ namespace clang {
       }
 
       ~RedeclarableResult() {
-        if (FirstID && Owning && isRedeclarableDeclKind(DeclKind) &&
-            Reader.PendingDeclChainsKnown.insert(FirstID).second)
-          Reader.PendingDeclChains.push_back(FirstID);
+        if (FirstID && Owning && isRedeclarableDeclKind(DeclKind)) {
+          auto Canon = Reader.GetDecl(FirstID)->getCanonicalDecl();
+          if (Reader.PendingDeclChainsKnown.insert(Canon).second)
+            Reader.PendingDeclChains.push_back(Canon);
+        }
       }
 
       /// \brief Retrieve the first ID.
@@ -160,12 +159,6 @@ namespace clang {
       /// \brief Get a known declaration that this should be merged with, if
       /// any.
       Decl *getKnownMergeTarget() const { return MergeWith; }
-
-      /// \brief Do not introduce this declaration ID into the set of pending
-      /// declaration chains.
-      void suppress() {
-        Owning = false;
-      }
     };
 
     /// \brief Class used to capture the result of searching for an existing
@@ -2076,12 +2069,14 @@ ASTDeclReader::VisitRedeclarable(Redeclarable<T> *D) {
   // and is used for space optimization.
   if (FirstDeclID == 0)
     FirstDeclID = ThisDeclID;
-  else if (Record[Idx++]) {
-    // We need to merge with FirstDeclID. Read it now to ensure that it is
-    // before us in the redecl chain, then forget we saw it so that we will
-    // merge with it.
-    MergeWith = Reader.GetDecl(FirstDeclID);
-    FirstDeclID = ThisDeclID;
+  else if (unsigned N = Record[Idx++]) {
+    // We have some declarations that must be before us in our redeclaration
+    // chain. Read them now, and remember that we ought to merge with one of
+    // them.
+    // FIXME: Provide a known merge target to the second and subsequent such
+    // declaration.
+    for (unsigned I = 0; I != N; ++I)
+      MergeWith = ReadDecl(Record, Idx/*, MergeWith*/);
   }
 
   T *FirstDecl = cast_or_null<T>(Reader.GetDecl(FirstDeclID));
@@ -2109,17 +2104,6 @@ void ASTDeclReader::mergeRedeclarable(Redeclarable<T> *DBase,
                                       RedeclarableResult &Redecl,
                                       DeclID TemplatePatternID) {
   T *D = static_cast<T*>(DBase);
-  T *DCanon = D->getCanonicalDecl();
-  if (D != DCanon &&
-      // IDs < NUM_PREDEF_DECL_IDS are not loaded from an AST file.
-      Redecl.getFirstID() >= NUM_PREDEF_DECL_IDS &&
-      (!Reader.getContext().getLangOpts().Modules ||
-       Reader.getOwningModuleFile(DCanon) == Reader.getOwningModuleFile(D))) {
-    // All redeclarations between this declaration and its originally-canonical
-    // declaration get pulled in when we load DCanon; we don't need to
-    // perform any more merging now.
-    Redecl.suppress();
-  }
 
   // If modules are not available, there is no reason to perform this merge.
   if (!Reader.getContext().getLangOpts().Modules)
@@ -2215,10 +2199,9 @@ void ASTDeclReader::mergeRedeclarable(Redeclarable<T> *DBase, T *Existing,
     // that. We accept the linear algorithm here because the number of
     // unique canonical declarations of an entity should always be tiny.
     if (DCanon == D) {
-      SmallVectorImpl<DeclID> &Merged = Reader.MergedDecls[ExistingCanon];
-      if (std::find(Merged.begin(), Merged.end(), Redecl.getFirstID())
-            == Merged.end())
-        Merged.push_back(Redecl.getFirstID());
+      Reader.MergedDecls[ExistingCanon].push_back(Redecl.getFirstID());
+      if (Reader.PendingDeclChainsKnown.insert(ExistingCanon).second)
+        Reader.PendingDeclChains.push_back(ExistingCanon);
     }
   }
 }
@@ -2697,8 +2680,6 @@ ASTDeclReader::FindExistingResult ASTDeclReader::findExisting(NamedDecl *D) {
     // unmergeable contexts.
     FindExistingResult Result(Reader, D, /*Existing=*/nullptr,
                               AnonymousDeclNumber, TypedefNameForLinkage);
-    // FIXME: We may still need to pull in the redeclaration chain; there can
-    // be redeclarations via 'decltype'.
     Result.suppress();
     return Result;
   }
@@ -2930,29 +2911,6 @@ void ASTReader::markIncompleteDeclChain(Decl *D) {
   }
 }
 
-ASTReader::MergedDeclsMap::iterator
-ASTReader::combineStoredMergedDecls(Decl *Canon, GlobalDeclID CanonID) {
-  // If we don't have any stored merged declarations, just look in the
-  // merged declarations set.
-  StoredMergedDeclsMap::iterator StoredPos = StoredMergedDecls.find(CanonID);
-  if (StoredPos == StoredMergedDecls.end())
-    return MergedDecls.find(Canon);
-
-  // Append the stored merged declarations to the merged declarations set.
-  MergedDeclsMap::iterator Pos = MergedDecls.find(Canon);
-  if (Pos == MergedDecls.end())
-    Pos = MergedDecls.insert(std::make_pair(Canon,
-                                            SmallVector<DeclID, 2>())).first;
-  Pos->second.append(StoredPos->second.begin(), StoredPos->second.end());
-  StoredMergedDecls.erase(StoredPos);
-
-  // Sort and uniquify the set of merged declarations.
-  llvm::array_pod_sort(Pos->second.begin(), Pos->second.end());
-  Pos->second.erase(std::unique(Pos->second.begin(), Pos->second.end()),
-                    Pos->second.end());
-  return Pos;
-}
-
 /// \brief Read the declaration at the given offset from the AST file.
 Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   unsigned Index = ID - NUM_PREDEF_DECL_IDS;
@@ -3362,25 +3320,25 @@ namespace {
   };
 }
 
-void ASTReader::loadPendingDeclChain(serialization::GlobalDeclID ID) {
-  Decl *D = GetDecl(ID);  
-  Decl *CanonDecl = D->getCanonicalDecl();
-  
+void ASTReader::loadPendingDeclChain(Decl *CanonDecl) {
+  // The decl might have been merged into something else after being added to
+  // our list. If it was, just skip it.
+  if (!CanonDecl->isCanonicalDecl())
+    return;
+
   // Determine the set of declaration IDs we'll be searching for.
-  SmallVector<DeclID, 1> SearchDecls;
-  GlobalDeclID CanonID = 0;
-  if (D == CanonDecl) {
-    SearchDecls.push_back(ID); // Always first.
-    CanonID = ID;
-  }
-  MergedDeclsMap::iterator MergedPos = combineStoredMergedDecls(CanonDecl, ID);
+  SmallVector<DeclID, 16> SearchDecls;
+  GlobalDeclID CanonID = CanonDecl->getGlobalID();
+  if (CanonID)
+    SearchDecls.push_back(CanonDecl->getGlobalID()); // Always first.
+  MergedDeclsMap::iterator MergedPos = MergedDecls.find(CanonDecl);
   if (MergedPos != MergedDecls.end())
     SearchDecls.append(MergedPos->second.begin(), MergedPos->second.end());
-  
+
   // Build up the list of redeclarations.
   RedeclChainVisitor Visitor(*this, SearchDecls, RedeclsDeserialized, CanonID);
   ModuleMgr.visitDepthFirst(&RedeclChainVisitor::visit, &Visitor);
-  
+
   // Retrieve the chains.
   ArrayRef<Decl *> Chain = Visitor.getChain();
   if (Chain.empty())