https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65509
--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
The following (untested) should work:
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -6113,6 +6113,7 @@ make_rtl_for_nonlocal_decl (tree decl, tree init, const
char* asmspec)
not emitted into the object file unnecessarily. */
filename = LOCATION_FILE (input_location);
if (!DECL_VIRTUAL_P (decl)
+ && !DECL_DECLARED_CONSTEXPR_P (decl)
&& TREE_READONLY (decl)
&& DECL_INITIAL (decl) != NULL_TREE
&& DECL_INITIAL (decl) != error_mark_node
My reasoning is that we shouldn't defer assembling the variable if it might be
needed in the constexpr context.