[Bug middle-end/85090] [8 Regression] wrong code with -O2 -fno-tree-dominator-opts -mavx512f -fira-algorithm=priority

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85090

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 43802
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43802&action=edit
gcc8-pr85090-wip.patch

Untested WIP; some more work is needed to get rid of the useless vextracti32x4
$0, ... insns, similarly e.g. how vec_extract_lo_v32hi deals with it.  Dunno if
we want in some way suggest to RA that it is less costly to use a dup operand
in that case.