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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/115055] reassociation should use
 match-and-simplify
Date: Mon, 13 May 2024 09:49:05 +0000
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X-Bugzilla-Component: tree-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115055

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2024-05-13
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
  b_5 =3D a_3(D) & c_4(D);
  _1 =3D a_3(D) =3D=3D 0;
  _2 =3D (int) _1;
  _6 =3D b_5 & _2;
  return _6;

I believe reassoc doesn't see that a and (int)(a =3D=3D 0) are "related" wh=
en
ranking ops of the AND, so it fails to appropriately order them and thus
trigger the simplification.  We definitely want to avoid doing n^2
matching combos of all AND operands.

So confirmed, but not necessarily confirming the proposed solution.=