* decl2.c (decl_constant_var_p): New fn.

	* decl2.c (decl_constant_var_p): New fn.
	(decl_maybe_constant_var_p): New fn.
	(mark_used): Rework instantiation of things needed for constant
	expressions.
	* cp-tree.h: Declare new fns.
	* pt.c (instantiate_decl): Handle cp_unevaluated_operand.
	(always_instantiate_p): Use decl_maybe_constant_var_p.
	(instantiate_decl): Don't defer constexpr functions.
	* repo.c (repo_emit_p): Use decl_maybe_constant_var_p.
	* semantics.c (finish_id_expression): Use decl_constant_var_p.
	Check for valid name in constant expr after mark_used.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@166164 138bc75d-0d04-0410-961f-82ee72b054a4