Store latest redeclaration for each redeclarable template declaration

This patch adds a Latest field to RedeclarableTemplateDecl's CommonBase
class which is used to store the latest redeclaration.

llvm-svn: 109755

clang/include/clang/AST/DeclTemplate.h

@@ -492,10 +492,7 @@ class RedeclarableTemplateDecl : public TemplateDecl {
 
   RedeclarableTemplateDecl *getCanonicalDeclImpl();
 
-  void setPreviousDeclarationImpl(RedeclarableTemplateDecl *Prev) {
+  void setPreviousDeclarationImpl(RedeclarableTemplateDecl *Prev);
-    if (Prev)
-      CommonOrPrev = Prev;
-  }
 
   RedeclarableTemplateDecl *getInstantiatedFromMemberTemplateImpl() {
     return getCommonPtr()->InstantiatedFromMember.getPointer();
@@ -517,6 +514,9 @@ protected:
     /// was explicitly specialized.
     llvm::PointerIntPair<RedeclarableTemplateDecl*, 1, bool>
       InstantiatedFromMember;
+
+    /// \brief The latest declaration of this template.
+    RedeclarableTemplateDecl *Latest;
   };
 
   /// \brief A pointer to the previous declaration (if this is a redeclaration)
@@ -602,6 +602,7 @@ public:
   }
 
   friend class PCHDeclReader;
+  friend class PCHDeclWriter;
 };
 
 template <class decl_type>

clang/lib/AST/DeclTemplate.cpp

@@ -94,6 +94,7 @@ RedeclarableTemplateDecl::CommonBase *RedeclarableTemplateDecl::getCommonPtr() {
   if (First->CommonOrPrev.isNull()) {
     CommonBase *CommonPtr = First->newCommon();
     First->CommonOrPrev = CommonPtr;
+    CommonPtr->Latest = First;
   }
   return First->CommonOrPrev.get<CommonBase*>();
 }
@@ -106,6 +107,18 @@ RedeclarableTemplateDecl *RedeclarableTemplateDecl::getCanonicalDeclImpl() {
   return Tmpl;
 }
 
+void RedeclarableTemplateDecl::setPreviousDeclarationImpl(
+                                               RedeclarableTemplateDecl *Prev) {
+  if (Prev) {
+    CommonBase *Common = Prev->getCommonPtr();
+    Prev = Common->Latest;
+    Common->Latest = this;
+    CommonOrPrev = Prev;
+  } else {
+    assert(CommonOrPrev.is<CommonBase*>() && "Cannot reset TemplateDecl Prev");
+  }
+}
+
 //===----------------------------------------------------------------------===//
 // FunctionTemplateDecl Implementation
 //===----------------------------------------------------------------------===//

clang/lib/Frontend/PCHReaderDecl.cpp

@@ -915,6 +915,11 @@ void PCHDeclReader::VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D) {
       if (Record[Idx++])
         D->setMemberSpecialization();
     }
+
+    RedeclarableTemplateDecl *LatestDecl = 
+        cast_or_null<RedeclarableTemplateDecl>(Reader.GetDecl(Record[Idx++]));
+    assert(LatestDecl->getKind() == D->getKind() && "Latest kind mismatch");
+    D->getCommonPtr()->Latest = LatestDecl;
   }
 }
 

clang/lib/Frontend/PCHWriterDecl.cpp

@@ -852,6 +852,8 @@ void PCHDeclWriter::VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D) {
     Writer.AddDeclRef(D->getInstantiatedFromMemberTemplate(), Record);
     if (D->getInstantiatedFromMemberTemplate())
       Record.push_back(D->isMemberSpecialization());
+
+    Writer.AddDeclRef(D->getCommonPtr()->Latest, Record);
   }
 }