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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug lto/106499] LTO runs forever in libfabric 1.15.1 linking
Date: Mon, 01 Aug 2022 23:21:14 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106499

--- Comment #12 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Tomasz K=C5=82oczko from comment #11)
> (In reply to Andrew Pinski from comment #10)
> > The flatten attribute is designed to override all heuristics in the com=
piler
> > that is designed to not cause the gignatic memory usage and compile tim=
e.
> > Basically you told the compiler to ignore those.
>=20
> Now I'm a bit confused because in this case looks like use flatten attrib=
ute
> caused high memory usage.
> Does it mean that (generally) flatten should not be used at the same time
> with inline?

The flatten attribute combined with LTO causes the high memory usage.
Flatten means inline everything into that function and ignore heuristics th=
at
might otherwise block the inlining.
Basically this means flatten should not be used combined with LTO. With LTO=
 you
could just allow the heuristics do its job and back off as needed.=