[Bug tree-optimization/81611] [8 Regression] gcc un-learned loop / post-increment optimization

[aoliva at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81611

--- Comment #5 from Alexandre Oliva <aoliva at gcc dot gnu.org> ---
Created attachment 42968
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42968&action=edit
partial candidate patch

Alas, although it restores good code for x86_64 and arm, it doesn't go as far
as enabling avr to use auto_inc (though auto_inc use is restored on arm). 
Still looking...