[Bug tree-optimization/80702] FRE fails to eliminate to leader dominating after unreachable edge removal

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80702

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2020-02-14
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1
      Known to fail|                            |10.0

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Re-confirmed at -O2.  The -O1 greedy mode get's this correct (it eliminates
on-the-fly):

  <bb 2> :
  _1 = a_5(D) + b_6(D);
  c = _1;
  _3 = a_5(D) * 2;
  c = _3;
  return _3;

re-writing the -O2/PRE elimination RPO style with RPO availability is possible
(but the avail tracking is a bit more expensive).