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From: "law at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/103226] [12 Regression] Recent change to
 copy-headers causes execution failure for gcc.dg/torture/pr80974
Date: Sat, 20 Nov 2021 07:10:55 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103226

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P1                          |P4

--- Comment #20 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Your c#19 was a bit hard to follow.  But you hit the key issue.  Namely that
the doloop pattern will set/clobber the condition codes if it gets split.=20
Failure to show that clobber means that IRA/LRA have incorrect dataflow and
make incorrect decisions.

I'm testing the obvious fix of adding the clobber.  It may be possible to
improve on my patch, but I'll leave that to someone who really cares about =
the
port.=