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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/108552] Linux i386 kernel 5.14 memory
 corruption for pre_compound_page() when gcov is enabled
Date: Mon, 30 Jan 2023 07:05:28 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108552

--- Comment #41 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Linus Torvalds from comment #31)
> (In reply to Richard Biener from comment #26)
> >=20
> > Now, in principle we should have applied store-motion and not only PRE =
which
> > would have avoided the issue, not tricking the RA into reloading the va=
lue
> > from where we store it in the loop, but the kernel uses -fno-tree-loop-=
im,
> > preventing that.  If you enable that you'd get
>=20
> Note that we use -fno-tree-loop-im only for the GCOV case, and because of
> another problem with code generation with gcov. See
>=20
>   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D69702
>=20
> and the fix for the excessive stack use was to disable that compiler opti=
on.
> See
>=20
>=20=20
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/
> ?id=3Dc87bf431448b404a6ef5fbabd74c0e3e42157a7f
>=20
> for the kernel commit message.

Yes, I remember.  So another option would be to add -fno-tree-pre to that
mix which should avoid hoisting the load out of the loop.=