diff --git a/gcc/cp/config-lang.in b/gcc/cp/config-lang.in
index da70b358413..4f5f8eca130 100644
--- a/gcc/cp/config-lang.in
+++ b/gcc/cp/config-lang.in
@@ -47,7 +47,7 @@ gtfiles="\
 \$(srcdir)/cp/friend.c \
 \$(srcdir)/cp/init.c \
 \$(srcdir)/cp/lambda.c \$(srcdir)/cp/lex.c \$(srcdir)/cp/logic.cc \
-\$(srcdir)/cp/mangle.c \$(srcdir)/cp/method.c \
+\$(srcdir)/cp/mangle.c \$(srcdir)/cp/method.c \$(srcdir)/cp/module.cc \
 \$(srcdir)/cp/name-lookup.c \
 \$(srcdir)/cp/parser.c \$(srcdir)/cp/pt.c \
 \$(srcdir)/cp/rtti.c \
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index b13c9d9f73d..6d8158a66f0 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -4964,6 +4964,11 @@ c_parse_final_cleanups (void)
       instantiate_pending_templates (retries);
       ggc_collect ();
 
+      if (header_module_p ())
+	/* A header modules initializations are handled in its
+	   importer.  */
+	continue;
+
       /* Write out virtual tables as required.  Writing out the
 	 virtual table for a template class may cause the
 	 instantiation of members of that class.  If we write out
@@ -5162,6 +5167,8 @@ c_parse_final_cleanups (void)
 	reconsider = true;
     }
 
+  finish_module_processing (parse_in);
+
   lower_var_init ();
 
   generate_mangling_aliases ();
@@ -5177,6 +5184,10 @@ 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 ())
 	  /* Don't complain if the template was defined.  */
 	  && !(DECL_TEMPLATE_INSTANTIATION (decl)
 	       && DECL_INITIAL (DECL_TEMPLATE_RESULT
@@ -5210,9 +5221,8 @@ c_parse_final_cleanups (void)
     splay_tree_foreach (priority_info_map,
 			generate_ctor_and_dtor_functions_for_priority,
 			/*data=*/&locus_at_end_of_parsing);
-  else if (c_dialect_objc () && objc_static_init_needed_p ())
-    /* If this is obj-c++ and we need a static init, call
-       generate_ctor_or_dtor_function.  */
+  else if ((c_dialect_objc () && objc_static_init_needed_p ())
+	   || module_initializer_kind ())
     generate_ctor_or_dtor_function (/*constructor_p=*/true,
 				    DEFAULT_INIT_PRIORITY,
 				    &locus_at_end_of_parsing);
diff --git a/gcc/cp/lambda.c b/gcc/cp/lambda.c
index 1a1647f465e..f6746d7304b 100644
--- a/gcc/cp/lambda.c
+++ b/gcc/cp/lambda.c
@@ -1114,6 +1114,8 @@ maybe_add_lambda_conv_op (tree type)
     while (src)
       {
 	tree new_node = copy_node (src);
+	/* We set DECL_CONTEXT of NEW_NODE to the statfn below.
+	   Notice this is creating a recursive type!  */
 
 	/* Clear TREE_ADDRESSABLE on thunk arguments.  */
 	TREE_ADDRESSABLE (new_node) = 0;
@@ -1393,6 +1395,12 @@ record_lambda_scope (tree lambda)
 {
   LAMBDA_EXPR_EXTRA_SCOPE (lambda) = lambda_scope;
   LAMBDA_EXPR_DISCRIMINATOR (lambda) = lambda_count++;
+  if (lambda_scope)
+    {
+      tree closure = LAMBDA_EXPR_CLOSURE (lambda);
+      gcc_checking_assert (closure);
+      maybe_attach_decl (lambda_scope, TYPE_NAME (closure));
+    }
 }
 
 /* This lambda is an instantiation of a lambda in a template default argument
diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 2417d67ee41..d8012d75ca4 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -154,11 +154,21 @@ set_originating_module (tree, bool)
 {
 }
 
+void
+maybe_attach_decl (tree, tree)
+{
+}
+
 void
 lazy_load_binding (unsigned, tree, tree, binding_slot *)
 {
 }
 
+void
+lazy_load_specializations (tree)
+{
+}
+
 void
 lazy_load_members (tree)
 {
@@ -216,6 +226,11 @@ maybe_check_all_macros (cpp_reader *)
 {
 }
 
+void
+finish_module_processing (cpp_reader *)
+{
+}
+
 void
 fini_modules ()
 {
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 6b8e486a642..e5f18d23ea0 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -9788,6 +9788,15 @@ lookup_template_class_1 (tree d1, tree arglist, tree in_decl, tree context,
 	return error_mark_node;
 
       gen_tmpl = most_general_template (templ);
+      if (modules_p ())
+	{
+	  tree origin = get_originating_module_decl (gen_tmpl);
+	  load_pending_specializations (CP_DECL_CONTEXT (origin),
+					DECL_NAME (origin));
+	  if (DECL_MODULE_PENDING_SPECIALIZATIONS_P (gen_tmpl))
+	    lazy_load_specializations (gen_tmpl);
+	}
+
       parmlist = DECL_TEMPLATE_PARMS (gen_tmpl);
       parm_depth = TMPL_PARMS_DEPTH (parmlist);
       arg_depth = TMPL_ARGS_DEPTH (arglist);
@@ -20907,6 +20916,15 @@ instantiate_template_1 (tree tmpl, tree orig_args, tsubst_flags_t complain)
 		(DECL_TI_ARGS (DECL_TEMPLATE_RESULT (tmpl)),
 		 targ_ptr));
 
+  if (modules_p ())
+    {
+      tree origin = get_originating_module_decl (gen_tmpl);
+      load_pending_specializations (CP_DECL_CONTEXT (origin),
+				    DECL_NAME (origin));
+      if (DECL_MODULE_PENDING_SPECIALIZATIONS_P (gen_tmpl))
+	lazy_load_specializations (gen_tmpl);
+    }
+
   /* It would be nice to avoid hashing here and then again in tsubst_decl,
      but it doesn't seem to be on the hot path.  */
   spec = retrieve_specialization (gen_tmpl, targ_ptr, 0);
diff --git a/gcc/gcc.c b/gcc/gcc.c
index 1d32375f648..d179de7d97f 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -1232,6 +1232,7 @@ static const char *cpp_unique_options =
  %{MD:-MD %{!o:%b.d}%{o*:%.d%*}}\
  %{MMD:-MMD %{!o:%b.d}%{o*:%.d%*}}\
  %{M} %{MM} %{MF*} %{MG} %{MP} %{MQ*} %{MT*}\
+ %{Mmodules} %{Mno-modules}\
  %{!E:%{!M:%{!MM:%{!MT:%{!MQ:%{MD|MMD:%{o*:-MQ %*}}}}}}}\
  %{remap} %{%:debug-level-gt(2):-dD}\
  %{!iplugindir*:%{fplugin*:%:find-plugindir()}}\
diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index e457b917b98..a89f063ab55 100644
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -773,6 +773,10 @@ enum tree_index {
   TI_SAT_UDA_TYPE,
   TI_SAT_UTA_TYPE,
 
+  TI_MODULE_HWM,
+  /* Nodes below here change during compilation, and should therefore
+     not be in the C++ module's global tree table.  */
+
   TI_OPTIMIZATION_DEFAULT,
   TI_OPTIMIZATION_CURRENT,
   TI_TARGET_OPTION_DEFAULT,