[Bug tree-optimization/89595] [8/9 Regression] DOM miscompiles code

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89595

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
           Priority|P3                          |P2
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2019-03-05
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
   Target Milestone|---                         |8.4
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
I have a patch.

Note to trigger the issue there has to be a free SSA name in the queue to
not run into

value_range *
vr_values::get_value_range (const_tree var)
{
...
  /* If we query the range for a new SSA name return an unmodifiable VARYING.
     We should get here at most from the substitute-and-fold stage which
     will never try to change values.  */
  if (ver >= num_vr_values)
    return CONST_CAST (value_range *, &vr_const_varying);