[Bug rtl-optimization/56766] Fails to combine (vec_select (vec_concat ...)) to (vec_merge ...)

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56766

--- Comment #6 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Richard Biener from comment #3)

> We still need to fixup the sse3_addsubv2df3 pattern or fix combine to try
> multiple "canonical" forms of vec_merge vs. (vec_select (vec_concat ...)).
> Or decide which one is canonical (I'd prefer simply dropping vec_merge - with
> AVX512 we've run out of bits for the CONST_INT selector....)

Does the attached patch work for you?

(Please note, that AVX512 does not implement 512bit ADDSUB insn.)