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From: "wilco at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/110061] libatomic: 128-bit atomics should be lock-free
 on AArch64
Date: Fri, 02 Jun 2023 21:23:09 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110061

--- Comment #14 from Wilco <wilco at gcc dot gnu.org> ---
(In reply to Wilco from comment #13)
> (In reply to Xi Ruoyao from comment #12)
> > (In reply to Wilco from comment #11)
> >=20
> > > > Then the compiler (and the standard) is not what they consider.  Su=
ch
> > > > misunderstandings are everywhere and this has no difference.
> > >=20
> > > Where is int128 in "the standard"?
> >=20
> > Consider this:
> >=20
> > const _Atomic long double x =3D 0.1;
> >=20
> > int main()
> > {
> > 	double y =3D x;
> > 	return y !=3D 0.1;
> > }
> >=20
> > If CAS is used here, the program will just segfault.  Does the standard=
 say
> > this is ill-formed or not?
>=20
> I'd say this is ill formed yes. And it will crash on Atom laptops.

Correction - it crashes on all AMD cpus too. Are you going to file bugrepor=
ts
for this?=