[PATCH] D154774: [Sema] Respect instantiated-from template's VisibilityAttr for two implicit/explicit instantiation cases

[Fangrui Song via Phabricator via cfe-commits]

MaskRay created this revision.
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In CodeGenCXX/visibility.cpp,

Match GCC for part of test51: Change explicit instantiation of a function
template to respect the instantiated-from template's VisibilityAttr.

Match GCC for test71: For an implicit or explicit instantiation of a class
template, change its member template instantiation to respect the
instantiated-from member template's VisibilityAttr.
Fix https://github.com/llvm/llvm-project/issues/31462


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D154774

Files:
  clang/lib/AST/Decl.cpp
  clang/test/CodeGenCXX/visibility.cpp


Index: clang/test/CodeGenCXX/visibility.cpp
===================================================================
--- clang/test/CodeGenCXX/visibility.cpp
+++ clang/test/CodeGenCXX/visibility.cpp
@@ -969,10 +969,6 @@
 }
 
 namespace test51 {
-  // Test that we use the visibility of struct foo when instantiating the
-  // template. Note that is a case where we disagree with gcc, it produces
-  // a default symbol.
-
   struct HIDDEN foo {
   };
   DEFAULT foo x, y, z;
@@ -980,8 +976,8 @@
   void DEFAULT zed() {
   }
   template void zed<&x>();
-  // CHECK-LABEL: define weak_odr hidden void @_ZN6test513zedIXadL_ZNS_1xEEEEEvv
-  // CHECK-HIDDEN-LABEL: define weak_odr hidden void @_ZN6test513zedIXadL_ZNS_1xEEEEEvv
+  // CHECK-LABEL: define weak_odr void @_ZN6test513zedIXadL_ZNS_1xEEEEEvv
+  // CHECK-HIDDEN-LABEL: define weak_odr void @_ZN6test513zedIXadL_ZNS_1xEEEEEvv
 
   template void HIDDEN zed<&y>();
   // CHECK-LABEL: define weak_odr hidden void @_ZN6test513zedIXadL_ZNS_1yEEEEEvv(
@@ -1373,6 +1369,7 @@
   template <class T> template <class U>
   U foo<T>::bar() { return {}; }
 
+  /// foo<int>::{zed,bar} get the instantiated-from member's HIDDEN, overriding DEFAULT.
   extern template struct DEFAULT foo<int>;
 
   int use() {
@@ -1380,13 +1377,12 @@
     foo<long> p;
     return o.zed() + o.bar<int>() + p.zed() + p.bar<int>();
   }
-  /// FIXME: foo<int>::bar is hidden in GCC w/ or w/o -fvisibility=hidden.
   // CHECK-LABEL: declare hidden noundef i32 @_ZN6test713fooIiE3zedEv(
-  // CHECK-LABEL: define linkonce_odr noundef i32 @_ZN6test713fooIiE3barIiEET_v(
+  // CHECK-LABEL: define linkonce_odr hidden noundef i32 @_ZN6test713fooIiE3barIiEET_v(
   // CHECK-LABEL: define linkonce_odr hidden noundef i64 @_ZN6test713fooIlE3zedEv(
-  // CHECK-LABEL: define linkonce_odr noundef i32 @_ZN6test713fooIlE3barIiEET_v(
+  // CHECK-LABEL: define linkonce_odr hidden noundef i32 @_ZN6test713fooIlE3barIiEET_v(
   // CHECK-HIDDEN-LABEL: declare hidden noundef i32 @_ZN6test713fooIiE3zedEv(
-  // CHECK-HIDDEN-LABEL: define linkonce_odr noundef i32 @_ZN6test713fooIiE3barIiEET_v(
+  // CHECK-HIDDEN-LABEL: define linkonce_odr hidden noundef i32 @_ZN6test713fooIiE3barIiEET_v(
   // CHECK-HIDDEN-LABEL: define linkonce_odr hidden noundef i64 @_ZN6test713fooIlE3zedEv(
   // CHECK-HIDDEN-LABEL: define linkonce_odr hidden noundef i32 @_ZN6test713fooIlE3barIiEET_v(
 }
Index: clang/lib/AST/Decl.cpp
===================================================================
--- clang/lib/AST/Decl.cpp
+++ clang/lib/AST/Decl.cpp
@@ -375,7 +375,9 @@
   if (!specInfo->isExplicitInstantiationOrSpecialization())
     return true;
 
-  return !fn->hasAttr<VisibilityAttr>();
+  return !fn->hasAttr<VisibilityAttr>() && !specInfo->getTemplate()
+                                                ->getTemplatedDecl()
+                                                ->hasAttr<VisibilityAttr>();
 }
 
 /// Merge in template-related linkage and visibility for the given
@@ -1240,12 +1242,20 @@
   }
   // Also handle function template specializations.
   if (const auto *fn = dyn_cast<FunctionDecl>(ND)) {
-    // If the function is a specialization of a template with an
-    // explicit visibility attribute, use that.
-    if (FunctionTemplateSpecializationInfo *templateInfo
-          = fn->getTemplateSpecializationInfo())
-      return getVisibilityOf(templateInfo->getTemplate()->getTemplatedDecl(),
-                             kind);
+    // If the function is a specialization of a template,
+    if (FunctionTemplateSpecializationInfo *templateInfo =
+            fn->getTemplateSpecializationInfo()) {
+      // ... If the template has an explicit visibility attribute, use that.
+      if (auto Vis = getVisibilityOf(
+              templateInfo->getTemplate()->getTemplatedDecl(), kind))
+        return Vis;
+      // ... If the template instantiates from a member template with an
+      // explicit visibility attribute, use that.
+      if (auto *A =
+              templateInfo->getTemplate()->getInstantiatedFromMemberTemplate())
+        return getVisibilityOf(A->getTemplatedDecl(), kind);
+      return std::nullopt;
+    }
 
     // If the function is a member of a specialization of a class template
     // and the corresponding decl has explicit visibility, use that.


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