r215786 - Make sure that vtables referenced from delay-parsed templates get referenced.

[Nico Weber]

Author: nico
Date: Fri Aug 15 18:21:41 2014
New Revision: 215786

URL: http://llvm.org/viewvc/llvm-project?rev=215786&view=rev
Log:
Make sure that vtables referenced from delay-parsed templates get referenced.

This fixes PR20671, see the bug for details. In short, ActOnTranslationUnit()
calls DefineUsedVTables() and only then PerformPendingInstantiations(). But
PerformPendingInstantiations() is what does delayed template parsing, so
vtables only references from late-parsed templates weren't marked used.

As a fix, move the SavePendingInstantiationsAndVTableUsesRAII in
PerformPendingInstantiations() up above the delayed template parsing code.
That way, vtables referenced from templates end up in the RAII object, and the
call to DefineUsedVTables() in PerformPendingInstantiations() marks them used.

Added:
    cfe/trunk/test/CodeGenCXX/microsoft-abi-structors-delayed-template.cpp
Modified:
    cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp

Modified: cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp?rev=215786&r1=215785&r2=215786&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp (original)
+++ cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp Fri Aug 15 18:21:41 2014
@@ -3319,6 +3319,20 @@ void Sema::InstantiateFunctionDefinition
     return;
   }
 
+  // If we're performing recursive template instantiation, create our own
+  // queue of pending implicit instantiations that we will instantiate later,
+  // while we're still within our own instantiation context.
+  // This has to happen before LateTemplateParser below is called, so that
+  // it marks vtables used in late parsed templates as used.
+  SavePendingLocalImplicitInstantiationsRAII
+      SavedPendingLocalImplicitInstantiations(*this);
+  std::unique_ptr<SavePendingInstantiationsAndVTableUsesRAII>
+      SavePendingInstantiationsAndVTableUses;
+  if (Recursive) {
+    SavePendingInstantiationsAndVTableUses.reset(
+        new SavePendingInstantiationsAndVTableUsesRAII(*this));
+  }
+
   // Call the LateTemplateParser callback if there is a need to late parse
   // a templated function definition.
   if (!Pattern && PatternDecl->isLateTemplateParsed() &&
@@ -3350,6 +3364,7 @@ void Sema::InstantiateFunctionDefinition
       Function->setInvalidDecl();
     } else if (Function->getTemplateSpecializationKind()
                  == TSK_ExplicitInstantiationDefinition) {
+      assert(!Recursive);
       PendingInstantiations.push_back(
         std::make_pair(Function, PointOfInstantiation));
     }
@@ -3386,18 +3401,6 @@ void Sema::InstantiateFunctionDefinition
   // Copy the inner loc start from the pattern.
   Function->setInnerLocStart(PatternDecl->getInnerLocStart());
 
-  // If we're performing recursive template instantiation, create our own
-  // queue of pending implicit instantiations that we will instantiate later,
-  // while we're still within our own instantiation context.
-  SavePendingLocalImplicitInstantiationsRAII
-      SavedPendingLocalImplicitInstantiations(*this);
-  std::unique_ptr<SavePendingInstantiationsAndVTableUsesRAII>
-      SavePendingInstantiationsAndVTableUses;
-  if (Recursive) {
-    SavePendingInstantiationsAndVTableUses.reset(
-        new SavePendingInstantiationsAndVTableUsesRAII(*this));
-  }
-
   EnterExpressionEvaluationContext EvalContext(*this,
                                                Sema::PotentiallyEvaluated);
 

Added: cfe/trunk/test/CodeGenCXX/microsoft-abi-structors-delayed-template.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/microsoft-abi-structors-delayed-template.cpp?rev=215786&view=auto
==============================================================================
--- cfe/trunk/test/CodeGenCXX/microsoft-abi-structors-delayed-template.cpp (added)
+++ cfe/trunk/test/CodeGenCXX/microsoft-abi-structors-delayed-template.cpp Fri Aug 15 18:21:41 2014
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -emit-llvm -fdelayed-template-parsing -std=c++11 -o - -triple=i386-pc-win32 %s > %t
+// RUN: FileCheck %s < %t
+
+// PR20671
+namespace vtable_referenced_from_template {
+struct ImplicitCtor {
+  virtual ~ImplicitCtor();
+};
+template <class T> void foo(T t) { new ImplicitCtor; }
+void bar() { foo(0); }
+// CHECK: store {{.*}} @"\01??_7ImplicitCtor at vtable_referenced_from_template@@6B@"
+}