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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/102989] Implement C2x's n2763 (_BitInt)
Date: Wed, 24 May 2023 14:57:15 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102989

--- Comment #48 from rguenther at suse dot de <rguenther at suse dot de> ---
> Am 24.05.2023 um 16:18 schrieb jakub at gcc dot gnu.org <gcc-bugzilla@gcc=
.gnu.org>:
>=20
> =EF=BB=BFhttps://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102989
>=20
> --- Comment #47 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> But then the pass effectively has to do lifetime analysis of the _BitInt(=
N) for
> N > 128 etc. SSA_NAMEs and perform the partitioning of those SSA_NAMEs in=
to
> VAR_DECLs/PARM_DECLs/RESULT_DECLs, so that we don't blow away the local s=
tack;
> perhaps as you wrote with some local subgraphs turned into a loop which w=
ill
> handle multiple operations together instead of just one operation per loo=
p.
> Or just use different VAR_DECLs but stick in clobbers where they will be =
dead
> and hope out of ssa can merge those.
> Anyway, more work than I hoped.
> Though, perhaps it can be also done incrementally, with bare minimum firs=
t and
> improvements later.

Sure, this is just what I think users will expect.  We don=E2=80=99t have t=
he high
level infrastructure to do this afterwards such as loop fusion and variable
contraction (well, in theory graphite can do it but even there we lack actu=
al
transform bits).=