[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 #23 from Uroš Bizjak <ubizjak at gmail dot com> ---
Created attachment 35768
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35768&action=edit
Testcase

Testcases, compile with "-O2 -ftree-vectorize -mavx".