[Bug tree-optimization/94500] Wrong maximum value with small integer types and AVX-512

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94500

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 48214
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48214&action=edit
gcc8-pr94500.patch

Untested fix.  Richi's r265004 commit has been an optimization which
essentially causes ix86_expand_reduc not to be called with these modes (but the
bug is still there if it were ever called with those modes).