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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/108657] csmith: possible wrong checksum with -O3 and
 -ftrivial-auto-var-init=zero
Date: Fri, 03 Feb 2023 18:47:11 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108657

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to David Binderman from comment #3)
> (In reply to Andrew Pinski from comment #2)
> > If I initialize __trans_tmp_13 explictly to 0, the issue goes away ....
>=20
> $ fgrep trans_tmp_13 bug880.c
>            int64_t __trans_tmp_13;
>                            (g_452) ^=3D (__trans_tmp_13);
> $=20
>=20
> This now looks like a bug in csmith.

It might be both. I have not looked into the IR differences with respect of
initializing and not initializing it and using/not using
-ftrivial-auto-var-init=3Dzero yet. This was mostly to give a hint to the n=
ext
person who looks into this issue to see if they understand why there is a
difference happening.
-ftrivial-auto-var-init=3Dzero should produce the similar results to initia=
lizing
that variable to 0 but it is not. There has been some bugs (in GCC) recentl=
y in
the area of not executed pathes with uninitialized variables changing the
behavior (incorrectly) so it might be related to one of those ...=