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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/102902] [12 Regression] -O3 produces code
 that uses an uninitialized variable but originally was not used by r12-3876
Date: Mon, 17 Jan 2022 13:09:36 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102902

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1

--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
PR100810 is P1 so lets make this one, too.  Just to say, the bug will be ve=
ry
difficult to fix for good because fundamentally a default def SSA looks
like to have the same value for two different uses but the way we handle it
means that guarantee is violated.  It's difficult to cure that not only bec=
ause
former defs can become undefs.  We'd need a way to stabilize the value on
an uninit use but without sacrifying optimization (for uses in PHI nodes).=