From 2a34df32641bf80bc67cda915afbe46552cad9dc Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Wed, 6 Jan 2010 22:00:56 +0000
Subject: [PATCH] Fix linkage for RTTI names by re-using the logic for
 computing the linkage of vtables. Before this, we were emitting RTTI names
 for template instantiations with strong external linkage rather than with
 weak ODR linkage.

llvm-svn: 92857
---
 clang/lib/CodeGen/CGRTTI.cpp        | 21 ++------------
 clang/lib/CodeGen/CodeGenModule.cpp | 45 ++++++++++++++---------------
 clang/lib/CodeGen/CodeGenModule.h   |  3 +-
 3 files changed, 26 insertions(+), 43 deletions(-)

diff --git a/clang/lib/CodeGen/CGRTTI.cpp b/clang/lib/CodeGen/CGRTTI.cpp
index 20e5fcec5684..29552ce4441c 100644
--- a/clang/lib/CodeGen/CGRTTI.cpp
+++ b/clang/lib/CodeGen/CGRTTI.cpp
@@ -360,27 +360,12 @@ static llvm::GlobalVariable::LinkageTypes getTypeInfoLinkage(QualType Ty) {
     // If we're in an anonymous namespace, then we always want internal linkage.
     if (RD->isInAnonymousNamespace() || !RD->hasLinkage())
       return llvm::GlobalVariable::InternalLinkage;
-    
+
+    // If this class does not have a vtable, we want weak linkage.
     if (!RD->isDynamicClass())
       return llvm::GlobalValue::WeakODRLinkage;
     
-    // Get the key function.
-    const CXXMethodDecl *KeyFunction = RD->getASTContext().getKeyFunction(RD);
-    if (!KeyFunction) {
-      // There is no key function, the RTTI descriptor is emitted with weak_odr
-      // linkage.
-      return llvm::GlobalValue::WeakODRLinkage;
-    }
-
-    // If the key function is defined, but inlined, then the RTTI descriptor is
-    // emitted with weak_odr linkage.
-    const FunctionDecl* KeyFunctionDefinition;
-    if (KeyFunction->getBody(KeyFunctionDefinition) &&
-        KeyFunctionDefinition->isInlined())
-      return llvm::GlobalValue::WeakODRLinkage;
-      
-    // Otherwise, the RTTI descriptor is emitted with external linkage.
-    return llvm::GlobalValue::ExternalLinkage;
+    return CodeGenModule::getVtableLinkage(RD);
   }
 
   case Type::Vector:
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index e0e8c54434e5..0dbf336dccc0 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -889,18 +889,17 @@ void CodeGenModule::EmitTentativeDefinition(const VarDecl *D) {
 
 llvm::GlobalVariable::LinkageTypes 
 CodeGenModule::getVtableLinkage(const CXXRecordDecl *RD) {
-  // Get the key function.
-  const CXXMethodDecl *KeyFunction = getContext().getKeyFunction(RD);
-  
-  if (KeyFunction) {
+  if (RD->isInAnonymousNamespace() || !RD->hasLinkage())
+    return llvm::GlobalVariable::InternalLinkage;
+
+  if (const CXXMethodDecl *KeyFunction
+                                    = RD->getASTContext().getKeyFunction(RD)) {
+    // If this class has a key function, use that to determine the linkage of
+    // the vtable.
     const FunctionDecl *Def = 0;
     if (KeyFunction->getBody(Def))
       KeyFunction = cast<CXXMethodDecl>(Def);
-  }
-  
-  if (RD->isInAnonymousNamespace() || !RD->hasLinkage())
-    return llvm::GlobalVariable::InternalLinkage;
-  else if (KeyFunction) {
+    
     switch (KeyFunction->getTemplateSpecializationKind()) {
       case TSK_Undeclared:
       case TSK_ExplicitSpecialization:
@@ -919,22 +918,20 @@ CodeGenModule::getVtableLinkage(const CXXRecordDecl *RD) {
         //      return llvm::GlobalVariable::AvailableExternallyLinkage;
         return llvm::GlobalVariable::WeakODRLinkage;
     }
-  } else if (KeyFunction) {
+  }
+  
+  switch (RD->getTemplateSpecializationKind()) {
+  case TSK_Undeclared:
+  case TSK_ExplicitSpecialization:
+  case TSK_ImplicitInstantiation:
+  case TSK_ExplicitInstantiationDefinition:
+    return llvm::GlobalVariable::WeakODRLinkage;
+    
+  case TSK_ExplicitInstantiationDeclaration:
+    // FIXME: Use available_externally linkage. However, this currently
+    // breaks LLVM's build due to undefined symbols.
+    //   return llvm::GlobalVariable::AvailableExternallyLinkage;
     return llvm::GlobalVariable::WeakODRLinkage;
-  } else {
-    switch (RD->getTemplateSpecializationKind()) {
-      case TSK_Undeclared:
-      case TSK_ExplicitSpecialization:
-      case TSK_ImplicitInstantiation:
-      case TSK_ExplicitInstantiationDefinition:
-        return llvm::GlobalVariable::WeakODRLinkage;
-        
-      case TSK_ExplicitInstantiationDeclaration:
-        // FIXME: Use available_externally linkage. However, this currently
-        // breaks LLVM's build due to undefined symbols.
-        //   return llvm::GlobalVariable::AvailableExternallyLinkage;
-        return llvm::GlobalVariable::WeakODRLinkage;
-    }
   }
   
   // Silence GCC warning.
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 575b518767e2..8f165109f5b0 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -409,7 +409,8 @@ public:
 
   /// getVtableLinkage - Return the appropriate linkage for the vtable, VTT,
   /// and type information of the given class.
-  llvm::GlobalVariable::LinkageTypes getVtableLinkage(const CXXRecordDecl *RD);
+  static llvm::GlobalVariable::LinkageTypes 
+  getVtableLinkage(const CXXRecordDecl *RD);
   
 private:
   /// UniqueMangledName - Unique a name by (if necessary) inserting it into the