[Bug tree-optimization/69595] [6 Regression] Bogus -Warray-bound warning due to missed optimization

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69595

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2016-02-01
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
So VRP doesn't detect the block is unreachable:

_6 = sysnum_4(D) < 0;
Found new range for _6: [0, +INF]
interesting_ssa_edges: adding SSA use in _8 = _6 | _7;
marking stmt to be not simulated again

Visiting statement:
_7 = sysnum_4(D) >= 0;
Found new range for _7: [0, +INF]
marking stmt to be not simulated again

Visiting statement:
_8 = _6 | _7;
Applying pattern match.pd:796, gimple-match.c:164
Found new range for _8: [0, +INF]
interesting_ssa_edges: adding SSA use in if (_8 != 0)

the old issue having to decide between using an integer range or a symbolic
range for a non-assert range we derive (as equivalences are keyed to specific
SSA names and we only have one here, _6).