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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/101001] [9/10/11/12 Regression] wrong code at
 -O3 on x86_64-linux-gnu
Date: Thu, 10 Jun 2021 07:26:08 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101001

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-06-10
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
         Depends on|                            |100934

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
We end up with

  <bb 2> [count: 0]:
  b.1_18 =3D{v} b;
  b.1_5 =3D{v} b;
...
  b.1_1 =3D{v} b;
  __builtin_unreachable ();

}

sounds related to PR100934, "fixed" with -fdisable-tree-cunroll.

Loop 1 iterates at most 15 times.
Loop 1 likely iterates at most 15 times.

-fdisable-tree-thread2 "fixes" it as well.  Likely a duplicate.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100934
[Bug 100934] [9/10/11/12 Regression] wrong code at -O3 during unrolling sin=
ce
r9-6299=