https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93080
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
comment#4 could be implemented by an associating pattern in match.pd, currently
we get
a_3 = BIT_INSERT_EXPR <a_1(D), c_2(D), 32 (32 bits)>;
a_4 = VEC_PERM_EXPR <a_3, a_1(D), { 0, 1, 6, 3 }>;
associating a VEC_PERM_EXPR <a, b, { ... }> when a or b are defined as
insertion into b or a respectively so we get a permute of either a
or b with itself (and in this case it's a noop permute).
Of course with an arbitrary sequence of inserts / extracts / permutes
more "generic" association would be necessary and a pure implementation
in match.pd looks difficult.
