c++: Support thread_local statics in header modules [PR113292]

Currently, thread_locals in header modules cause ICEs. This patch makes
the required changes for them to work successfully.

This requires additionally writing the DECL_TLS_MODEL for thread-local
variables to the module interface, and the TLS wrapper function needs to
have its DECL_BEFRIENDING_CLASSES written too as this is used to
retrieve what VAR_DECL it's a wrapper for when emitting a definition at
end of TU processing.

	PR c++/113292

gcc/cp/ChangeLog:
	* decl2.cc (get_tls_wrapper_fn): Set DECL_CONTEXT.
	(c_parse_final_cleanups): Suppress warning for no definition of
	TLS wrapper functions in header modules.
	* module.cc (trees_out::lang_decl_vals): Write wrapped variable
	for TLS wrapper functions.
	(trees_in::lang_decl_vals): Read it.
	(trees_out::decl_value): Write TLS model for thread-local vars.
	(trees_in::decl_value): Read it for new decls. Remember to emit
	definitions of TLS wrapper functions later.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/pr113292_a.H: New test.
	* g++.dg/modules/pr113292_b.C: New test.
	* g++.dg/modules/pr113292_c.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>

gcc/cp/decl2.cc

@@ -3897,6 +3897,7 @@ get_tls_wrapper_fn (tree var)
       TREE_PUBLIC (fn) = TREE_PUBLIC (var);
       DECL_ARTIFICIAL (fn) = true;
       DECL_IGNORED_P (fn) = 1;
+      DECL_CONTEXT (fn) = DECL_CONTEXT (var);
       /* The wrapper is inline and emitted everywhere var is used.  */
       DECL_DECLARED_INLINE_P (fn) = true;
       if (TREE_PUBLIC (var))
@@ -5326,10 +5327,11 @@ c_parse_final_cleanups (void)
 	     #pragma interface, etc.) we decided not to emit the
 	     definition here.  */
 	  && !DECL_INITIAL (decl)
-	  /* A defaulted fn in a header module can be synthesized on
-	     demand later.  (In non-header modules we should have
-	     synthesized it above.)  */
-	  && !(DECL_DEFAULTED_FN (decl) && header_module_p ())
+	  /* A defaulted fn or TLS wrapper in a header module can be
+	     synthesized on demand later.  (In non-header modules we
+	     should have synthesized it above.)  */
+	  && !(header_module_p ()
+	       && (DECL_DEFAULTED_FN (decl) || decl_tls_wrapper_p (decl)))
 	  /* Don't complain if the template was defined.  */
 	  && !(DECL_TEMPLATE_INSTANTIATION (decl)
 	       && DECL_INITIAL (DECL_TEMPLATE_RESULT

gcc/cp/module.cc

@@ -6950,6 +6950,9 @@ trees_out::lang_decl_vals (tree t)
 	  if (streaming_p ())
 	    wi (lang->u.fn.u5.fixed_offset);
 	}
+      else if (decl_tls_wrapper_p (t))
+	/* The wrapped variable.  */
+	WT (lang->u.fn.befriending_classes);
       else
 	WT (lang->u.fn.u5.cloned_function);
 
@@ -7029,6 +7032,8 @@ trees_in::lang_decl_vals (tree t)
 	  RT (lang->u.fn.befriending_classes);
 	  lang->u.fn.u5.fixed_offset = wi ();
 	}
+      else if (decl_tls_wrapper_p (t))
+	RT (lang->u.fn.befriending_classes);
       else
 	RT (lang->u.fn.u5.cloned_function);
 
@@ -7928,6 +7933,9 @@ trees_out::decl_value (tree decl, depset *dep)
 				   decl, cloned_p ? "" : "not ");
     }
 
+  if (streaming_p () && VAR_P (decl) && CP_DECL_THREAD_LOCAL_P (decl))
+    u (decl_tls_model (decl));
+
   if (streaming_p ())
     dump (dumper::TREE) && dump ("Written decl:%d %C:%N", tag,
 				 TREE_CODE (decl), decl);
@@ -8275,6 +8283,13 @@ trees_in::decl_value ()
 	   look like templates.  */
 	if (!install_implicit_member (inner))
 	  set_overrun ();
+
+      /* When importing a TLS wrapper from a header unit, we haven't
+	 actually emitted its definition yet. Remember it so we can
+	 do this later.  */
+      if (state->is_header ()
+	  && decl_tls_wrapper_p (decl))
+	note_vague_linkage_fn (decl);
     }
   else
     {
@@ -8358,6 +8373,13 @@ trees_in::decl_value ()
 	}
     }
 
+  if (VAR_P (decl) && CP_DECL_THREAD_LOCAL_P (decl))
+    {
+      enum tls_model model = tls_model (u ());
+      if (is_new)
+	set_decl_tls_model (decl, model);
+    }
+
   if (!NAMESPACE_SCOPE_P (inner)
       && ((TREE_CODE (inner) == TYPE_DECL
 	   && !is_typedef

gcc/testsuite/g++.dg/modules/pr113292_a.H

@@ -0,0 +1,34 @@
+// PR c++/113292
+// { dg-additional-options "-fmodule-header" }
+// { dg-module-cmi {} }
+
+struct test {
+  static const test& get_instance() {
+    return instance;
+  }
+  static thread_local test instance;
+};
+
+
+template <typename T>
+struct test_template {
+  static const test_template& get_instance() {
+    return instance;
+  }
+  static thread_local test_template instance;
+
+  template <typename U>
+  static const test_template& get_template_instance() {
+    return template_instance<U>;
+  }
+
+  template <typename U>
+  static thread_local test_template template_instance;
+};
+
+template <typename T>
+thread_local test_template<T> test_template<T>::instance;
+
+template <typename T>
+template <typename U>
+thread_local test_template<T> test_template<T>::template_instance;

gcc/testsuite/g++.dg/modules/pr113292_b.C

@@ -0,0 +1,13 @@
+// PR c++/113292
+// { dg-additional-options "-fmodules-ts" }
+
+import "pr113292_a.H";
+
+// provide a definition of 'instance' so things link
+thread_local test test::instance;
+
+void instantiate() {
+  auto& instance = test::get_instance();
+  auto& t_instance = test_template<int>::get_instance();
+  auto& tt_instance = test_template<int>::get_template_instance<double>();
+};

gcc/testsuite/g++.dg/modules/pr113292_c.C

@@ -0,0 +1,11 @@
+// PR c++/113292
+// { dg-module-do link }
+// { dg-additional-options "-fmodules-ts" }
+
+import "pr113292_a.H";
+
+int main() {
+  auto& instance = test::get_instance();
+  auto& t_instance = test_template<int>::get_instance();
+  auto& tt_instance = test_template<int>::get_template_instance<double>();
+}