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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/95643] Optimizer fails to realize that a
 variable tested twice in a row is the same both times
Date: Fri, 12 Jun 2020 07:33:46 +0000
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X-Bugzilla-Component: tree-optimization
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X-Bugzilla-Keywords: easyhack, missed-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95643

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2020-06-12
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |easyhack

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  value-numbering doesn't use the alternate assertion discovery
code and thus for the partly simplified condition does not record the
appropriate
expressions.  Likewise EVRP lacks simple forward-propagation during this
assertion discovery (value-numbering would also need that) in
register_edge_assert_for (where it tests for defs like a & b and a | b
it needs to look for a simple boolean re-test/inversion as well).

Should be easy to amend for this case.=