c++: Update TLS model after processing a TLS variable

Set a tentative TLS model in grokvardecl and update TLS mode with the
default TLS access model after a TLS variable has been fully processed
if the default TLS access model is stronger.

gcc/cp/

	PR c++/107393
	* decl.cc (grokvardecl): Set a tentative TLS model which will be
	updated by cplus_decl_attributes later.
	* decl2.cc (cplus_decl_attributes): Update TLS model with the
	default TLS access model if the default TLS access model is
	stronger.
	* pt.cc (tsubst_decl): Set TLS model only after processing a
	variable.

gcc/testsuite/

	PR c++/107393
	* g++.dg/tls/pr107393-1.C: New test.
	* g++.dg/tls/pr107393-2.C: Likewise.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>

5 files changed, 61 insertions, 4 deletions

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index f088d09..a6a9842 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -12183,8 +12183,11 @@ grokvardecl (tree type,
       if (DECL_EXTERNAL (decl) || TREE_STATIC (decl))
 	{
 	  CP_DECL_THREAD_LOCAL_P (decl) = true;
+	  // NB: Set a tentative TLS model to avoid tls_model attribute
+	  // warnings due to lack of thread storage duration.  It will
+	  // be updated by cplus_decl_attributes later.
 	  if (!processing_template_decl)
-	    set_decl_tls_model (decl, decl_default_tls_model (decl));
+	    set_decl_tls_model (decl, TLS_MODEL_REAL);
 	}
       if (declspecs->gnu_thread_keyword_p)
 	SET_DECL_GNU_TLS_P (decl);
diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index 6499be1..c9cca7b 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -2013,6 +2013,15 @@ cplus_decl_attributes (tree *decl, tree attributes, int flags)
 	if (*decl == pattern)
 	  TREE_UNAVAILABLE (tmpl) = true;
       }
+
+  if (VAR_P (*decl) && CP_DECL_THREAD_LOCAL_P (*decl))
+    {
+      // tls_model attribute can set a stronger TLS access model.
+      tls_model model = DECL_TLS_MODEL (*decl);
+      tls_model default_model = decl_default_tls_model (*decl);
+      if (default_model > model)
+	set_decl_tls_model (*decl, default_model);
+    }
 }
 
 /* Walks through the namespace- or function-scope anonymous union
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 365a6c5..7f0d16f 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -16034,9 +16034,6 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain,
 				       == TYPE_MAIN_VARIANT (type));
 		SET_DECL_VALUE_EXPR (r, ve);
 	      }
-	    if (CP_DECL_THREAD_LOCAL_P (r)
-		&& !processing_template_decl)
-	      set_decl_tls_model (r, decl_default_tls_model (r));
 	  }
 	else if (DECL_SELF_REFERENCE_P (t))
 	  SET_DECL_SELF_REFERENCE_P (r);
@@ -16099,6 +16096,11 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain,
 	      register_local_specialization (r, t);
 	  }
 
+	if (VAR_P (r)
+	    && CP_DECL_THREAD_LOCAL_P (r)
+	    && !processing_template_decl)
+	  set_decl_tls_model (r, decl_default_tls_model (r));
+
 	DECL_CHAIN (r) = NULL_TREE;
 
 	if (!apply_late_template_attributes (&r, DECL_ATTRIBUTES (r),
diff --git a/gcc/testsuite/g++.dg/tls/pr107393-1.C b/gcc/testsuite/g++.dg/tls/pr107393-1.C
new file mode 100644
index 0000000..644b4f4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tls/pr107393-1.C
@@ -0,0 +1,14 @@
+// { dg-do compile { target c++11 } }
+// { dg-require-effective-target fpic }
+// { dg-require-effective-target tls }
+// { dg-options "-O2 -fno-pic -fdump-ipa-whole-program" }
+// { dg-add-options tls }
+
+struct Dtor;
+template <typename> struct X { static thread_local Dtor m; };
+template <typename T> thread_local Dtor X<T>::m;
+extern template Dtor X<char>::m;
+void *e2 = &X<char>::m;
+
+// tls_model should be tls-initial-exec due to extern template.
+// { dg-final { scan-ipa-dump "Varpool flags: tls-initial-exec" "whole-program" } }
diff --git a/gcc/testsuite/g++.dg/tls/pr107393-2.C b/gcc/testsuite/g++.dg/tls/pr107393-2.C
new file mode 100644
index 0000000..6a69800
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tls/pr107393-2.C
@@ -0,0 +1,29 @@
+// { dg-do compile }
+// { dg-require-effective-target fpic }
+// { dg-require-effective-target tls }
+// { dg-options "-O2 -fno-pic -fdump-ipa-whole-program" }
+// { dg-add-options tls }
+
+template<class T>
+struct S {
+  static __thread int i;
+};
+
+template<class T>
+__thread int S<T>::i;
+
+extern template
+__thread int S<void>::i;
+
+int &vi()
+{
+  return S<void>::i;
+}
+
+int &ci()
+{
+  return S<char>::i;
+}
+
+// tls_model should be tls-initial-exec due to extern template.
+// { dg-final { scan-ipa-dump "Varpool flags: tls-initial-exec" "whole-program" } }