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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/114787] [13/14 Regression] wrong code at -O1
 on x86_64-linux-gnu (the generated code hangs)
Date: Wed, 24 Apr 2024 06:12:19 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114787

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot =
gnu.org
             Status|NEW                         |ASSIGNED

--- Comment #14 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jan Hubicka from comment #13)
> -fdump-tree-all-all  changing generated code is also bad.  We probably
> should avoid dumping loop bounds then they are not recorded. I added dump=
ing
> of loop bounds and this may be unexpected side effect. WIll take a look.

I think consistently estimating the number of iterations here is correct.

I don't think the bug should be P1, it's latent and exposed only with an
artificial testcase.  We've likely had similar bugs before where we end up
associating estimates with a wrong loop after some CFG transform.

In this case we end up with the i-loop header being associated with a former
irreducible region.  The fix in the past was to release estimates/niters
on problematic transforms.  Let me have a look.=