Extend the hidden-visibility vtables optimization to template classes that

haven't been explicitly instantiated.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@110189 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 42 insertions, 18 deletions

diff --git a/lib/CodeGen/CGVTables.cpp b/lib/CodeGen/CGVTables.cpp
index 052a6fdca3..9cb64c6d5b 100644
--- a/lib/CodeGen/CGVTables.cpp
+++ b/lib/CodeGen/CGVTables.cpp
@@ -2929,18 +2929,34 @@ CodeGenVTables::EmitVTableDefinition(llvm::GlobalVariable *VTable,
 
   // It's okay to have multiple copies of a vtable, so don't make the
   // dynamic linker unique them.  Suppress this optimization if it's
-  // possible that there might be unresolved references elsewhere,
-  // which can happen if
-  //   - there's a key function and the vtable is getting emitted weak
-  //     anyway for whatever reason
-  //   - there might be an explicit instantiation declaration somewhere,
-  //     i.e. if it's a template at all
+  // possible that there might be unresolved references elsewhere
+  // which can only be resolved by this emission.
   if (Linkage == llvm::GlobalVariable::WeakODRLinkage &&
       VTable->getVisibility() == llvm::GlobalVariable::DefaultVisibility &&
-      !RD->hasAttr<VisibilityAttr>() &&
-      RD->getTemplateSpecializationKind() == TSK_Undeclared &&
-      !CGM.Context.getKeyFunction(RD)) {
-    VTable->setVisibility(llvm::GlobalVariable::HiddenVisibility);
+      !RD->hasAttr<VisibilityAttr>()) {
+    switch (RD->getTemplateSpecializationKind()) {
+
+    // Every use of a non-template or explicitly-specialized class's
+    // vtable has to emit it.
+    case TSK_ExplicitSpecialization:
+    case TSK_Undeclared:
+    // Implicit instantiations can ignore the possibility of an
+    // explicit instantiation declaration because there necessarily
+    // must be an EI definition somewhere with default visibility.
+    case TSK_ImplicitInstantiation:
+      // If there's a key function, there may be translation units
+      // that don't have the key function's definition.
+      if (!CGM.Context.getKeyFunction(RD))
+        // Otherwise, drop the visibility to hidden.
+        VTable->setVisibility(llvm::GlobalValue::HiddenVisibility);
+      break;
+
+    // We have to disable the optimization if this is an EI definition
+    // because there might be EI declarations in other shared objects.
+    case TSK_ExplicitInstantiationDefinition:
+    case TSK_ExplicitInstantiationDeclaration:
+      break;
+    }
   }
 }
 
diff --git a/test/CodeGenCXX/mangle-subst-std.cpp b/test/CodeGenCXX/mangle-subst-std.cpp
index 9c1e978294..b08b12c91e 100644
--- a/test/CodeGenCXX/mangle-subst-std.cpp
+++ b/test/CodeGenCXX/mangle-subst-std.cpp
@@ -3,13 +3,13 @@
 // Check mangling of Vtables, VTTs, and construction vtables that
 // involve standard substitutions.
 
-// CHECK: @_ZTVSd = weak_odr constant 
+// CHECK: @_ZTVSd = weak_odr hidden constant 
 // CHECK: @_ZTCSd0_Si = internal constant 
 // CHECK: @_ZTCSd16_So = internal constant
 // CHECK: @_ZTTSd = weak_odr constant
-// CHECK: @_ZTVSo = weak_odr constant
+// CHECK: @_ZTVSo = weak_odr hidden constant
 // CHECK: @_ZTTSo = weak_odr constant
-// CHECK: @_ZTVSi = weak_odr constant
+// CHECK: @_ZTVSi = weak_odr hidden constant
 // CHECK: @_ZTTSi = weak_odr constant
 namespace std {
   struct A { A(); };
diff --git a/test/CodeGenCXX/virt-template-vtable.cpp b/test/CodeGenCXX/virt-template-vtable.cpp
index b955828312..ab406fd998 100644
--- a/test/CodeGenCXX/virt-template-vtable.cpp
+++ b/test/CodeGenCXX/virt-template-vtable.cpp
@@ -19,4 +19,4 @@ template class A<short>;
 // CHECK: @_ZTV1B = weak_odr hidden constant
 // CHECK: @_ZTV1AIlE = weak_odr constant
 // CHECK: @_ZTV1AIsE = weak_odr constant
-// CHECK: @_ZTV1AIiE = weak_odr constant
+// CHECK: @_ZTV1AIiE = weak_odr hidden constant
diff --git a/test/CodeGenCXX/vtable-linkage.cpp b/test/CodeGenCXX/vtable-linkage.cpp
index a4808d0b76..9b93a316be 100644
--- a/test/CodeGenCXX/vtable-linkage.cpp
+++ b/test/CodeGenCXX/vtable-linkage.cpp
@@ -11,6 +11,7 @@
 // RUN: FileCheck --check-prefix=CHECK-10 %s < %t
 // RUN: FileCheck --check-prefix=CHECK-11 %s < %t
 // RUN: FileCheck --check-prefix=CHECK-12 %s < %t
+// RUN: FileCheck --check-prefix=CHECK-13 %s < %t
 
 namespace {
   struct A {
@@ -83,12 +84,13 @@ struct F<char> {
 template struct F<short>;
 extern template struct F<int>;
 
-void use_F(F<char> &fc) {
+void use_F() {
+  F<char> fc;
+  fc.foo();
   F<int> fi;
   fi.foo();
   F<long> fl;
   (void)fl;
-  fc.foo();
 }
 
 // B has a key function that is not defined in this translation unit so its vtable
@@ -135,8 +137,8 @@ void use_F(F<char> &fc) {
 // CHECK-7: @_ZTI1EIlE = weak_odr constant
 
 // F<long> is an implicit template instantiation with no key function,
-// so its vtable should have weak_odr linkage.
-// CHECK-8: @_ZTV1FIlE = weak_odr constant
+// so its vtable should have weak_odr linkage and hidden visibility.
+// CHECK-8: @_ZTV1FIlE = weak_odr hidden constant
 // CHECK-8: @_ZTS1FIlE = weak_odr constant
 // CHECK-8: @_ZTI1FIlE = weak_odr constant
 
@@ -161,6 +163,12 @@ void use_F(F<char> &fc) {
 // CHECK-12: @_ZTSN12_GLOBAL__N_11AE = internal constant
 // CHECK-12: @_ZTIN12_GLOBAL__N_11AE = internal constant
 
+// F<char> is an explicit specialization without a key function, so
+// its vtable should have weak_odr linkage and hidden visibility.
+// CHECK-13: @_ZTV1FIcE = weak_odr hidden constant
+// CHECK-13: @_ZTS1FIcE = weak_odr constant
+// CHECK-13: @_ZTI1FIcE = weak_odr constant
+
 // RUN: FileCheck --check-prefix=CHECK-G %s < %t
 //
 // CHECK-G: @_ZTV1GIiE = weak_odr constant