https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68782
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Jason Merrill from comment #3)
> Hmm, any element without TREE_CONSTANT should have caused us to return
> the original CONSTRUCTOR.
Perhaps the TREE_SIDE_EFFECTS stuff is not needed, but for TREE_CONSTANT
perhaps the reason is that constexpr.c has different POV on what is a constant
compared to ../tree.c - at least it seems that cxx_eval_constant_expression
happily accepts &y->c as *non_constant_p = false, but if CONSTRUCTOR containing
that is marked TREE_CONSTANT (which is IMHO wrong, because in that case all
elements should be TREE_CONSTANT), then we e.g. trigger:
case CONSTRUCTOR:
if (TREE_CONSTANT (t))
/* Don't re-process a constant CONSTRUCTOR, but do fold it to
VECTOR_CST if applicable. */
return fold (t);
r = cxx_eval_bare_aggregate (ctx, t, lval,
non_constant_p, overflow_p);
break;
and just fold it instead of calling cxx_eval_bare_aggregate on it.
> I thought there was already a function to recompute these flags, but I'm
> not finding it.
I can't find it either, we have that only for ADDR_EXPR it seems -
recompute_tree_invariant_for_addr_expr.
