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From: "matz at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/88345] -Os overrides -falign-functions=N on the
 command line
Date: Wed, 06 Dec 2023 18:02:35 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D88345

--- Comment #21 from Michael Matz <matz at gcc dot gnu.org> ---
(In reply to Jan Hubicka from comment #20)
> >=20
> > Live patching (user-space) doesn't depend on any particular alignment of
> > functions, on x86-64 at least.  (The plan for other architectures would=
n't need
> > any specific alignment either).  Note that the above complaints about m=
issing
> > alignment is for kernel (!) ftrace/livepatching on arm64 (!), not on x8=
6_64.
>=20
> I had impression that x86-64 also needs forced alignment so the patching
> can be always done atomically.  But it is not a big practical difference
> if we go with a flag specifying minimal function alignment.

Not for userspace live patching (it's done while the process is stopped).
kernel live patching may or may not need it.  Point being that alignment
shouldn't be implied by the live patching options as its orthogonal.=