Implement proper linkage for explicit instantiation declarations of

inlined functions. For example, given

  template<typename T>
  class string {
    unsigned Len;

  public:
    unsigned size() const { return Len; }
  };

  extern template class string<char>;

we now give the instantiation of string<char>::size
available_externally linkage (if it is ever instantiated!), as
permitted by the C++0x standard.
      

llvm-svn: 85340

clang/lib/AST/Decl.cpp

@@ -643,10 +643,33 @@ unsigned FunctionDecl::getMinRequiredArguments() const {
 }
 
 bool FunctionDecl::isInlined() const {
-  return isInlineSpecified() || (isa<CXXMethodDecl>(this) && !isOutOfLine());
+  if (isInlineSpecified() || (isa<CXXMethodDecl>(this) && !isOutOfLine()))
+    return true;
+
+  switch (getTemplateSpecializationKind()) {
+  case TSK_Undeclared:
+  case TSK_ExplicitSpecialization:
+    return false;
+
+  case TSK_ImplicitInstantiation:
+  case TSK_ExplicitInstantiationDeclaration:
+  case TSK_ExplicitInstantiationDefinition:
+    // Handle below.
+    break;
+  }
+
+  const FunctionDecl *PatternDecl = getTemplateInstantiationPattern();
+  Stmt *Pattern = 0;
+  if (PatternDecl)
+    Pattern = PatternDecl->getBody(PatternDecl);
+  
+  if (Pattern && PatternDecl)
+    return PatternDecl->isInlined();
+  
+  return false;
 }
 
-/// \brief For an inline function definition in C, determine whether the 
+/// \brief For an inline function definition in C or C++, determine whether the 
 /// definition will be externally visible.
 ///
 /// Inline function definitions are always available for inlining optimizations.
@@ -666,8 +689,9 @@ bool FunctionDecl::isInlined() const {
 bool FunctionDecl::isInlineDefinitionExternallyVisible() const {
   assert(isThisDeclarationADefinition() && "Must have the function definition");
   assert(isInlined() && "Function must be inline");
+  ASTContext &Context = getASTContext();
   
-  if (!getASTContext().getLangOptions().C99 || hasAttr<GNUInlineAttr>()) {
+  if (!Context.getLangOptions().C99 || hasAttr<GNUInlineAttr>()) {
     // GNU inline semantics. Based on a number of examples, we came up with the
     // following heuristic: if the "inline" keyword is present on a
     // declaration of the function but "extern" is not present on that

clang/lib/CodeGen/CodeGenModule.cpp

@@ -253,6 +253,10 @@ GetLinkageForFunction(ASTContext &Context, const FunctionDecl *FD,
   if (FD->isInAnonymousNamespace())
     return CodeGenModule::GVA_Internal;
 
+  // "static" functions get internal linkage.
+  if (FD->getStorageClass() == FunctionDecl::Static && !isa<CXXMethodDecl>(FD))
+    return CodeGenModule::GVA_Internal;
+  
   // The kind of external linkage this function will have, if it is not
   // inline or static.
   CodeGenModule::GVALinkage External = CodeGenModule::GVA_StrongExternal;
@@ -260,18 +264,6 @@ GetLinkageForFunction(ASTContext &Context, const FunctionDecl *FD,
       FD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
     External = CodeGenModule::GVA_TemplateInstantiation;
 
-  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
-    // C++ member functions defined inside the class are always inline.
-    if (MD->isInlined())
-      return CodeGenModule::GVA_CXXInline;
-
-    return External;
-  }
-
-  // "static" functions get internal linkage.
-  if (FD->getStorageClass() == FunctionDecl::Static)
-    return CodeGenModule::GVA_Internal;
-
   if (!FD->isInlined())
     return External;
 
@@ -285,8 +277,16 @@ GetLinkageForFunction(ASTContext &Context, const FunctionDecl *FD,
     return CodeGenModule::GVA_C99Inline;
   }
 
-  // C++ inline semantics
-  assert(Features.CPlusPlus && "Must be in C++ mode");
+  // C++0x [temp.explicit]p9:
+  //   [ Note: The intent is that an inline function that is the subject of 
+  //   an explicit instantiation declaration will still be implicitly 
+  //   instantiated when used so that the body can be considered for 
+  //   inlining, but that no out-of-line copy of the inline function would be
+  //   generated in the translation unit. -- end note ]
+  if (FD->getTemplateSpecializationKind() 
+                                       == TSK_ExplicitInstantiationDeclaration)
+    return CodeGenModule::GVA_C99Inline;
+  
   return CodeGenModule::GVA_CXXInline;
 }
 

clang/test/CXX/temp/temp.spec/temp.explicit/p9-linkage.cpp

@@ -0,0 +1,66 @@
+// RUN: clang-cc -emit-llvm -std=c++0x -o - %s | FileCheck %s
+
+template<typename T>
+struct X0 {
+  void f(T &t) {
+    t = 0;
+  }
+  
+  void g(T &t);
+  
+  void h(T &t);
+  
+  static T static_var;
+};
+
+template<typename T>
+inline void X0<T>::g(T & t) {
+  t = 0;
+}
+
+template<typename T>
+void X0<T>::h(T & t) {
+  t = 0;
+}
+
+template<typename T>
+T X0<T>::static_var = 0;
+
+extern template struct X0<int*>;
+
+int *&test(X0<int*> xi, int *ip) {
+  // CHECK: define available_externally void @_ZN2X0IPiE1fERS0_
+  xi.f(ip);
+  // CHECK: define available_externally void @_ZN2X0IPiE1gERS0_
+  xi.g(ip);
+  // CHECK: declare void @_ZN2X0IPiE1hERS0_
+  xi.h(ip);
+  return X0<int*>::static_var;
+}
+
+template<typename T>
+void f0(T& t) {
+  t = 0;
+}
+
+template<typename T>
+inline void f1(T& t) {
+  t = 0;
+}
+
+extern template void f0<>(int *&);
+extern template void f1<>(int *&);
+
+void test_f0(int *ip, float *fp) {
+  // CHECK: declare void @_Z2f0IPiEvRT_
+  f0(ip);
+  // CHECK: define linkonce_odr void @_Z2f0IPfEvRT_
+  f0(fp);
+}
+
+void test_f1(int *ip, float *fp) {
+  // CHECK: define available_externally void @_Z2f1IPiEvRT_
+  f1(ip);
+  // CHECK: define linkonce_odr void @_Z2f1IPfEvRT_
+  f1(fp);
+}